Can I extend a class using more than 1 class in PHP

Question

If I have several classes with functions that I need but want to store separately for organisation  can I extend a class to have both   i e  class a extends b extends c  edit  I know how to extend classes one at a time  but I m looking for a method to instantly extend a class using multiple base classes - AFAIK you can t do this in PHP but there should be ways around it without resorting to class c extends b  class b extends a

User · Answer

I just solved my  multiple inheritance  problem with   class Session       public  username     class MyServiceResponsetype       protected  only avaliable in response     class SessionResponse extends MyServiceResponsetype           has shared  only avaliable in response         public  session       public function   construct Session  session           this- gt session    session             This way I have the power to manipulate session inside a SessionResponse which extends MyServiceResponsetype still being able to handle Session by itself

User · Answer

PHP does not allow multiple inheritance  but you can do with implementing multiple interfaces  If the implementation is  heavy   provide skeletal implementation for each interface in a seperate class  Then  you can delegate all interface class to these skeletal implementations via object containment

User · Answer

PHP does not yet support multiple class inheritance  it does however support multiple interface inheritance   See http   www hudzilla org php 6 17 0 php for some examples

User · Answer

If you really want to fake multiple inheritance in PHP 5 3  you can use the magic function   call    This is ugly though it works from class A user s point of view   class B       public function method from b  s            echo  s           class C       public function method from c  s            echo  s           class A extends B     private  c         public function   construct            this- gt c   new C                fake  quot extends C quot  using magic function   public function   call  method   args           this- gt c- gt  method  args 0             a   new A   a- gt method from b  quot abc quot     a- gt method from c  quot def quot     Prints  quot abcdef quot

User · Answer

Multiple inheritance seems to work at the interface level  I made a test on php 5 6 1   Here is a working code    lt  php   interface Animal       public function sayHello        interface HairyThing       public function plush       interface Dog extends Animal  HairyThing       public function bark        class Puppy implements Dog       public function bark                 echo  ouaf              public function sayHello                 echo  hello              public function plush                 echo  plush               echo PHP VERSION     5 6 1  o   new Puppy     o- gt bark     o- gt plush     o- gt sayHello       displays  5 6 16ouafplushhello   I didn t think that was possible  but I stumbled upon in the SwiftMailer source code  in the Swift Transport IoBuffer class  which has the following definition    interface Swift Transport IoBuffer extends Swift InputByteStream  Swift OutputByteStream   I didn t play with it yet  but I thought it might be interesting to share

User · Answer

I have read several articles discouraging inheritance in projects  as opposed to libraries frameworks   and encouraging to program agaisnt interfaces  no against implementations  They also advocate OO by composition  if you need the functions in class a and b  make c having members fields of this type   class C       private  a   b       public function   construct  x   y                 this- gt a   new A 42   x            this- gt b   new B  y              protected function DoSomething                  this- gt a- gt Act             this- gt b- gt Do

User · Answer

You could use traits  which  hopefully  will be available from PHP 5 4   Traits is a mechanism for code reuse in single inheritance languages such as PHP  A Trait is intended to reduce some limitations of single inheritance by enabling a developer to reuse sets of methods freely in several independent classes living in different class hierarchies  The semantics of the combination of Traits and classes is defined in a way  which reduces complexity and avoids the typical problems associated with multiple inheritance and Mixins   They are recognized for their potential in supporting better composition and reuse  hence their integration in newer versions of languages such as Perl 6  Squeak  Scala  Slate and Fortress  Traits have also been ported to Java and C    More information  https   wiki php net rfc traits

User · Answer

Always good idea is to make parent class  with functions     i e  add this all functionality to parent    And  move  all classes that use this hierarchically down  I need - rewrite functions  which are specific

User · Answer

I have read several articles discouraging inheritance in projects  as opposed to libraries frameworks   and encouraging to program agaisnt interfaces  no against implementations  They also advocate OO by composition  if you need the functions in class a and b  make c having members fields of this type   class C       private  a   b       public function   construct  x   y                 this- gt a   new A 42   x            this- gt b   new B  y              protected function DoSomething                  this- gt a- gt Act             this- gt b- gt Do

User · Answer

lt  php    what if we want to extend more than one class   abstract class ExtensionBridge          array containing all the extended classes     private   exts   array        public   this       function   construct      this    this        public function addExt  object                 this- gt  exts    object             public function   get  varname                foreach  this- gt  exts as  ext                        if property exists  ext  varname               return  ext- gt  varname                       public function   call  method  args                foreach  this- gt  exts as  ext                        if method exists  ext  method               return call user method array  method  ext  args                     throw new Exception  This Method   method  doesn t exists               class Ext1       private  name         private  id         public function setID  id   this- gt id    id       public function setName  name   this- gt name    name       public function getID   return  this- gt id       public function getName   return  this- gt name      class Ext2       private  address         private  country         public function setAddress  address   this- gt address    address       public function setCountry  country   this- gt country    country       public function getAddress   return  this- gt address       public function getCountry   return  this- gt country      class Extender extends ExtensionBridge       function   construct                 parent  addExt new Ext1             parent  addExt new Ext2                public function   toString                 return  this- gt getName      from     this- gt getCountry              o   new Extender     o- gt setName  Mahdi     o- gt setCountry  Al-Ahwaz    echo  o    gt

User · Answer

Not knowing exactly what you re trying to achieve  I would suggest looking into the possibility of redesigning you application to use composition rather than inheritance in this case

User · Answer

This is not a real answer  we have duplicate class      but it works     class A         do some things    class B         do some things     class copy B is copy all class B  class copy B extends A          do some things  copy class B     class A B extends copy B     now  class C A extends A   class C B extends B   class C A b extends A B      extends A  amp  B

User · Answer

If you really want to fake multiple inheritance in PHP 5 3  you can use the magic function   call    This is ugly though it works from class A user s point of view   class B       public function method from b  s            echo  s           class C       public function method from c  s            echo  s           class A extends B     private  c         public function   construct            this- gt c   new C                fake  quot extends C quot  using magic function   public function   call  method   args           this- gt c- gt  method  args 0             a   new A   a- gt method from b  quot abc quot     a- gt method from c  quot def quot     Prints  quot abcdef quot

User · Answer

class A extends B     class B extends C     Then A has extended both B and C

User · Answer

PHP does not allow multiple inheritance  but you can do with implementing multiple interfaces  If the implementation is  heavy   provide skeletal implementation for each interface in a seperate class  Then  you can delegate all interface class to these skeletal implementations via object containment

User · Answer

class A extends B     class B extends C     Then A has extended both B and C

User · Answer

You are able to do that using Traits in PHP which announced as of PHP 5 4  Here is a quick tutorial for you  http   culttt com 2014 06 25 php-traits

User · Answer

Always good idea is to make parent class  with functions     i e  add this all functionality to parent    And  move  all classes that use this hierarchically down  I need - rewrite functions  which are specific

User · Answer

Not knowing exactly what you re trying to achieve  I would suggest looking into the possibility of redesigning you application to use composition rather than inheritance in this case

User · Answer

Use traits as base classes  Then use them in a parent class  Extend it    trait business    function sell            function buy            function collectMoney            trait human      function think              function speak              class BusinessPerson    use business    use human       If you have more traits bring more     class BusinessWoman extends BusinessPerson      function getPregnant                bw   new BusinessWoman     bw - gt speak     bw- gt getPregnant      See now business woman logically inherited business and human both

User · Answer

PHP does not yet support multiple class inheritance  it does however support multiple interface inheritance   See http   www hudzilla org php 6 17 0 php for some examples

User · Answer

I have read several articles discouraging inheritance in projects  as opposed to libraries frameworks   and encouraging to program agaisnt interfaces  no against implementations  They also advocate OO by composition  if you need the functions in class a and b  make c having members fields of this type   class C       private  a   b       public function   construct  x   y                 this- gt a   new A 42   x            this- gt b   new B  y              protected function DoSomething                  this- gt a- gt Act             this- gt b- gt Do

User · Answer

There are plans for adding mix-ins soon  I believe   But until then  go with the accepted answer   You can abstract that out a bit to make an  extendable  class   class Extendable    private  extender array       public function addExtender Extender  obj        this- gt extenders      obj       obj- gt setExtendee  this          public function   call  name   params       foreach  this- gt extenders as  extender            do reflection to see if extender has this method with this argument count        if  method exists  extender   name              return call user func array array  extender   name    params                           foo   new Extendable     foo- gt addExtender new OtherClass      foo- gt other class method      Note that in this model  OtherClass  gets to  know  about  foo   OtherClass needs to have a public function called  setExtendee  to set up this relationship  Then  if it s methods are invoked from  foo  it can access  foo internally   It will not  however  get access to any private protected methods variables like a real extended class would

User · Answer

Classes are not meant to be just collections of methods  A class is supposed to represent an abstract concept  with both state  fields  and behaviour  methods  which changes the state  Using inheritance just to get some desired behaviour sounds like bad OO design  and exactly the reason why many languages disallow multiple inheritance  in order to prevent  spaghetti inheritance   i e  extending 3 classes because each has a method you need  and ending up with a class that inherits 100 method and 20 fields  yet only ever uses 5 of them

User · Answer

EDIT  2020 PHP 5 4  and 7  As of PHP 5 4 0 there are  quot Traits quot  - you can use more traits in one class  so the final deciding point would be whether you want really an inheritance or you just need some  quot feature quot  trait   Trait is  vaguely said  an already implemented interface that is meant to be just used   Currently accepted answer by  Franck will work but it is not in fact multiple inheritance but a child instance of class defined out of scope  also there is the    call    shorthand - consider using just    this- childInstance- method args   anywhere you need ExternalClass class method in  extended  class  Exact answer No you can t  respectively  not really  as manual of extends keyword says   An extended class is always dependent on a single base class  that is  multiple inheritance is not supported   Real answer However as  adam suggested correctly this does NOT forbids you to use multiple hierarchal inheritance  You CAN extend one class  with another and another with another and so on    So pretty simple example on this would be  class firstInheritance   class secondInheritance extends firstInheritance   class someFinalClass extends secondInheritance        and so on     Important note As you might have noticed  you can only do multiple 2   intehritance by hierarchy if you have control over all classes included in the process - that means  you can t apply this solution e g  with built-in classes or with classes you simply can t edit - if you want to do that  you are left with the  Franck solution - child instances     And finally example with some output  class A    function a hi        echo  quot I am a of A quot  PHP EOL  quot  lt br gt  quot  PHP EOL           class B extends A    function b hi        echo  quot I am b of B quot  PHP EOL  quot  lt br gt  quot  PHP EOL           class C extends B    function c hi        echo  quot I am c of C quot  PHP EOL  quot  lt br gt  quot  PHP EOL            myTestInstance   new C      myTestInstance- gt a hi     myTestInstance- gt b hi     myTestInstance- gt c hi     Which outputs I am a of A  I am b of B  I am c of C

User · Answer

You cannot have a class that extends two base classes  You could not have      this is NOT allowed  for all you google speeders  Matron extends Nurse  HumanEntity   You could however have a hierarchy as follows     Matron extends Nurse     Consultant extends Doctor  Nurse extends HumanEntity Doctor extends HumanEntity  HumanEntity extends DatabaseTable DatabaseTable extends AbstractTable   and so on

User · Answer

If you really want to fake multiple inheritance in PHP 5 3  you can use the magic function   call    This is ugly though it works from class A user s point of view   class B       public function method from b  s            echo  s           class C       public function method from c  s            echo  s           class A extends B     private  c         public function   construct            this- gt c   new C                fake  quot extends C quot  using magic function   public function   call  method   args           this- gt c- gt  method  args 0             a   new A   a- gt method from b  quot abc quot     a- gt method from c  quot def quot     Prints  quot abcdef quot

User · Answer

Multiple inheritance seems to work at the interface level  I made a test on php 5 6 1   Here is a working code    lt  php   interface Animal       public function sayHello        interface HairyThing       public function plush       interface Dog extends Animal  HairyThing       public function bark        class Puppy implements Dog       public function bark                 echo  ouaf              public function sayHello                 echo  hello              public function plush                 echo  plush               echo PHP VERSION     5 6 1  o   new Puppy     o- gt bark     o- gt plush     o- gt sayHello       displays  5 6 16ouafplushhello   I didn t think that was possible  but I stumbled upon in the SwiftMailer source code  in the Swift Transport IoBuffer class  which has the following definition    interface Swift Transport IoBuffer extends Swift InputByteStream  Swift OutputByteStream   I didn t play with it yet  but I thought it might be interesting to share

User · Answer

There are plans for adding mix-ins soon  I believe   But until then  go with the accepted answer   You can abstract that out a bit to make an  extendable  class   class Extendable    private  extender array       public function addExtender Extender  obj        this- gt extenders      obj       obj- gt setExtendee  this          public function   call  name   params       foreach  this- gt extenders as  extender            do reflection to see if extender has this method with this argument count        if  method exists  extender   name              return call user func array array  extender   name    params                           foo   new Extendable     foo- gt addExtender new OtherClass      foo- gt other class method      Note that in this model  OtherClass  gets to  know  about  foo   OtherClass needs to have a public function called  setExtendee  to set up this relationship  Then  if it s methods are invoked from  foo  it can access  foo internally   It will not  however  get access to any private protected methods variables like a real extended class would

User · Answer

Not knowing exactly what you re trying to achieve  I would suggest looking into the possibility of redesigning you application to use composition rather than inheritance in this case

User · Answer

You cannot have a class that extends two base classes  You could not have      this is NOT allowed  for all you google speeders  Matron extends Nurse  HumanEntity   You could however have a hierarchy as follows     Matron extends Nurse     Consultant extends Doctor  Nurse extends HumanEntity Doctor extends HumanEntity  HumanEntity extends DatabaseTable DatabaseTable extends AbstractTable   and so on

User · Answer

Classes are not meant to be just collections of methods  A class is supposed to represent an abstract concept  with both state  fields  and behaviour  methods  which changes the state  Using inheritance just to get some desired behaviour sounds like bad OO design  and exactly the reason why many languages disallow multiple inheritance  in order to prevent  spaghetti inheritance   i e  extending 3 classes because each has a method you need  and ending up with a class that inherits 100 method and 20 fields  yet only ever uses 5 of them

User · Answer

Not knowing exactly what you re trying to achieve  I would suggest looking into the possibility of redesigning you application to use composition rather than inheritance in this case

User · Answer

I just solved my  multiple inheritance  problem with   class Session       public  username     class MyServiceResponsetype       protected  only avaliable in response     class SessionResponse extends MyServiceResponsetype           has shared  only avaliable in response         public  session       public function   construct Session  session           this- gt session    session             This way I have the power to manipulate session inside a SessionResponse which extends MyServiceResponsetype still being able to handle Session by itself

User · Answer

Classes are not meant to be just collections of methods  A class is supposed to represent an abstract concept  with both state  fields  and behaviour  methods  which changes the state  Using inheritance just to get some desired behaviour sounds like bad OO design  and exactly the reason why many languages disallow multiple inheritance  in order to prevent  spaghetti inheritance   i e  extending 3 classes because each has a method you need  and ending up with a class that inherits 100 method and 20 fields  yet only ever uses 5 of them

User · Answer

If you want to check if a function is public see this topic   https   stackoverflow com a 4160928 2226755  And use call user func array      method for many or not arguments   Like this    class B       public function method from b  s            echo  s           class C       public function method from c  l   l1   l2            echo  l  l1  l2           class A extends B       private  c       public function   construct              this- gt c   new C             public function   call  method   args            if  method exists  this- gt c   method                  reflection   new ReflectionMethod  this- gt c   method               if    reflection- gt isPublic                      throw new RuntimeException  Call to not public method   get class  this      method                                 return call user func array array  this- gt c   method    args             else               throw new RuntimeException  Call to undefined method   get class  this      method                           a   new A   a- gt method from b  abc     a- gt method from c  d    e    f

User · Answer

PHP does not yet support multiple class inheritance  it does however support multiple interface inheritance   See http   www hudzilla org php 6 17 0 php for some examples

User · Answer

If you want to check if a function is public see this topic   https   stackoverflow com a 4160928 2226755  And use call user func array      method for many or not arguments   Like this    class B       public function method from b  s            echo  s           class C       public function method from c  l   l1   l2            echo  l  l1  l2           class A extends B       private  c       public function   construct              this- gt c   new C             public function   call  method   args            if  method exists  this- gt c   method                  reflection   new ReflectionMethod  this- gt c   method               if    reflection- gt isPublic                      throw new RuntimeException  Call to not public method   get class  this      method                                 return call user func array array  this- gt c   method    args             else               throw new RuntimeException  Call to undefined method   get class  this      method                           a   new A   a- gt method from b  abc     a- gt method from c  d    e    f

User · Answer

PHP does not allow multiple inheritance  but you can do with implementing multiple interfaces  If the implementation is  heavy   provide skeletal implementation for each interface in a seperate class  Then  you can delegate all interface class to these skeletal implementations via object containment

User · Answer

EDIT  2020 PHP 5 4  and 7  As of PHP 5 4 0 there are  quot Traits quot  - you can use more traits in one class  so the final deciding point would be whether you want really an inheritance or you just need some  quot feature quot  trait   Trait is  vaguely said  an already implemented interface that is meant to be just used   Currently accepted answer by  Franck will work but it is not in fact multiple inheritance but a child instance of class defined out of scope  also there is the    call    shorthand - consider using just    this- childInstance- method args   anywhere you need ExternalClass class method in  extended  class  Exact answer No you can t  respectively  not really  as manual of extends keyword says   An extended class is always dependent on a single base class  that is  multiple inheritance is not supported   Real answer However as  adam suggested correctly this does NOT forbids you to use multiple hierarchal inheritance  You CAN extend one class  with another and another with another and so on    So pretty simple example on this would be  class firstInheritance   class secondInheritance extends firstInheritance   class someFinalClass extends secondInheritance        and so on     Important note As you might have noticed  you can only do multiple 2   intehritance by hierarchy if you have control over all classes included in the process - that means  you can t apply this solution e g  with built-in classes or with classes you simply can t edit - if you want to do that  you are left with the  Franck solution - child instances     And finally example with some output  class A    function a hi        echo  quot I am a of A quot  PHP EOL  quot  lt br gt  quot  PHP EOL           class B extends A    function b hi        echo  quot I am b of B quot  PHP EOL  quot  lt br gt  quot  PHP EOL           class C extends B    function c hi        echo  quot I am c of C quot  PHP EOL  quot  lt br gt  quot  PHP EOL            myTestInstance   new C      myTestInstance- gt a hi     myTestInstance- gt b hi     myTestInstance- gt c hi     Which outputs I am a of A  I am b of B  I am c of C

User · Answer

Use traits as base classes  Then use them in a parent class  Extend it    trait business    function sell            function buy            function collectMoney            trait human      function think              function speak              class BusinessPerson    use business    use human       If you have more traits bring more     class BusinessWoman extends BusinessPerson      function getPregnant                bw   new BusinessWoman     bw - gt speak     bw- gt getPregnant      See now business woman logically inherited business and human both

User · Answer

You could use traits  which  hopefully  will be available from PHP 5 4   Traits is a mechanism for code reuse in single inheritance languages such as PHP  A Trait is intended to reduce some limitations of single inheritance by enabling a developer to reuse sets of methods freely in several independent classes living in different class hierarchies  The semantics of the combination of Traits and classes is defined in a way  which reduces complexity and avoids the typical problems associated with multiple inheritance and Mixins   They are recognized for their potential in supporting better composition and reuse  hence their integration in newer versions of languages such as Perl 6  Squeak  Scala  Slate and Fortress  Traits have also been ported to Java and C    More information  https   wiki php net rfc traits

User · Answer

One of the problems of PHP as a programming language is the fact that you can only have single inheritance  This means a class can only inherit from one other class   However  a lot of the time it would be beneficial to inherit from multiple classes  For example  it might be desirable to inherit methods from a couple of different classes in order to prevent code duplication   This problem can lead to class that has a long family history of inheritance which often does not make sense   In PHP 5 4 a new feature of the language was added known as Traits  A Trait is kind of like a Mixin in that it allows you to mix Trait classes into an existing class  This means you can reduce code duplication and get the benefits whilst avoiding the problems of multiple inheritance   Traits

User · Answer

One of the problems of PHP as a programming language is the fact that you can only have single inheritance  This means a class can only inherit from one other class   However  a lot of the time it would be beneficial to inherit from multiple classes  For example  it might be desirable to inherit methods from a couple of different classes in order to prevent code duplication   This problem can lead to class that has a long family history of inheritance which often does not make sense   In PHP 5 4 a new feature of the language was added known as Traits  A Trait is kind of like a Mixin in that it allows you to mix Trait classes into an existing class  This means you can reduce code duplication and get the benefits whilst avoiding the problems of multiple inheritance   Traits

User · Answer

I have read several articles discouraging inheritance in projects  as opposed to libraries frameworks   and encouraging to program agaisnt interfaces  no against implementations  They also advocate OO by composition  if you need the functions in class a and b  make c having members fields of this type   class C       private  a   b       public function   construct  x   y                 this- gt a   new A 42   x            this- gt b   new B  y              protected function DoSomething                  this- gt a- gt Act             this- gt b- gt Do

User · Answer

There are plans for adding mix-ins soon  I believe   But until then  go with the accepted answer   You can abstract that out a bit to make an  extendable  class   class Extendable    private  extender array       public function addExtender Extender  obj        this- gt extenders      obj       obj- gt setExtendee  this          public function   call  name   params       foreach  this- gt extenders as  extender            do reflection to see if extender has this method with this argument count        if  method exists  extender   name              return call user func array array  extender   name    params                           foo   new Extendable     foo- gt addExtender new OtherClass      foo- gt other class method      Note that in this model  OtherClass  gets to  know  about  foo   OtherClass needs to have a public function called  setExtendee  to set up this relationship  Then  if it s methods are invoked from  foo  it can access  foo internally   It will not  however  get access to any private protected methods variables like a real extended class would

User · Answer

If you really want to fake multiple inheritance in PHP 5 3  you can use the magic function   call    This is ugly though it works from class A user s point of view   class B       public function method from b  s            echo  s           class C       public function method from c  s            echo  s           class A extends B     private  c         public function   construct            this- gt c   new C                fake  quot extends C quot  using magic function   public function   call  method   args           this- gt c- gt  method  args 0             a   new A   a- gt method from b  quot abc quot     a- gt method from c  quot def quot     Prints  quot abcdef quot

User · Answer

You are able to do that using Traits in PHP which announced as of PHP 5 4  Here is a quick tutorial for you  http   culttt com 2014 06 25 php-traits

User · Answer

PHP does not yet support multiple class inheritance  it does however support multiple interface inheritance   See http   www hudzilla org php 6 17 0 php for some examples

User · Answer

lt  php    what if we want to extend more than one class   abstract class ExtensionBridge          array containing all the extended classes     private   exts   array        public   this       function   construct      this    this        public function addExt  object                 this- gt  exts    object             public function   get  varname                foreach  this- gt  exts as  ext                        if property exists  ext  varname               return  ext- gt  varname                       public function   call  method  args                foreach  this- gt  exts as  ext                        if method exists  ext  method               return call user method array  method  ext  args                     throw new Exception  This Method   method  doesn t exists               class Ext1       private  name         private  id         public function setID  id   this- gt id    id       public function setName  name   this- gt name    name       public function getID   return  this- gt id       public function getName   return  this- gt name      class Ext2       private  address         private  country         public function setAddress  address   this- gt address    address       public function setCountry  country   this- gt country    country       public function getAddress   return  this- gt address       public function getCountry   return  this- gt country      class Extender extends ExtensionBridge       function   construct                 parent  addExt new Ext1             parent  addExt new Ext2                public function   toString                 return  this- gt getName      from     this- gt getCountry              o   new Extender     o- gt setName  Mahdi     o- gt setCountry  Al-Ahwaz    echo  o    gt

User · Answer

There are plans for adding mix-ins soon  I believe   But until then  go with the accepted answer   You can abstract that out a bit to make an  extendable  class   class Extendable    private  extender array       public function addExtender Extender  obj        this- gt extenders      obj       obj- gt setExtendee  this          public function   call  name   params       foreach  this- gt extenders as  extender            do reflection to see if extender has this method with this argument count        if  method exists  extender   name              return call user func array array  extender   name    params                           foo   new Extendable     foo- gt addExtender new OtherClass      foo- gt other class method      Note that in this model  OtherClass  gets to  know  about  foo   OtherClass needs to have a public function called  setExtendee  to set up this relationship  Then  if it s methods are invoked from  foo  it can access  foo internally   It will not  however  get access to any private protected methods variables like a real extended class would

User · Answer

PHP does not allow multiple inheritance  but you can do with implementing multiple interfaces  If the implementation is  heavy   provide skeletal implementation for each interface in a seperate class  Then  you can delegate all interface class to these skeletal implementations via object containment

User · Answer

This is not a real answer  we have duplicate class      but it works     class A         do some things    class B         do some things     class copy B is copy all class B  class copy B extends A          do some things  copy class B     class A B extends copy B     now  class C A extends A   class C B extends B   class C A b extends A B      extends A  amp  B

User · Answer

Classes are not meant to be just collections of methods  A class is supposed to represent an abstract concept  with both state  fields  and behaviour  methods  which changes the state  Using inheritance just to get some desired behaviour sounds like bad OO design  and exactly the reason why many languages disallow multiple inheritance  in order to prevent  spaghetti inheritance   i e  extending 3 classes because each has a method you need  and ending up with a class that inherits 100 method and 20 fields  yet only ever uses 5 of them

User · Answer

You cannot have a class that extends two base classes  You could not have      this is NOT allowed  for all you google speeders  Matron extends Nurse  HumanEntity   You could however have a hierarchy as follows     Matron extends Nurse     Consultant extends Doctor  Nurse extends HumanEntity Doctor extends HumanEntity  HumanEntity extends DatabaseTable DatabaseTable extends AbstractTable   and so on

User · Answer

You cannot have a class that extends two base classes  You could not have      this is NOT allowed  for all you google speeders  Matron extends Nurse  HumanEntity   You could however have a hierarchy as follows     Matron extends Nurse     Consultant extends Doctor  Nurse extends HumanEntity Doctor extends HumanEntity  HumanEntity extends DatabaseTable DatabaseTable extends AbstractTable   and so on

[php] Can I extend a class using more than 1 class in PHP?

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