How do I create a copy of an object in PHP

Question

It appears that in PHP objects are passed by reference  Even assignment operators do not appear to be creating a copy of the Object   Here s a simple  contrived proof    lt  php  class A       public  b      function set b  obj     obj- gt b    after       a   new A     a- gt b    before    c    a    i would especially expect this to create a copy   set b  a    print  a- gt b    i would expect this to show  before  print  c- gt b    i would ESPECIALLY expect this to show  before     gt    In both print cases I am getting  after   So  how do I pass  a to set b   by value  not by reference

User · Accepted Answer

In PHP 5  objects are passed by reference  In PHP 4 they are passed by value  that s why it had runtime pass by reference  which became deprecated    You can use the  clone  operator in PHP5 to copy objects    objectB   clone  objectA    Also  it s just objects that are passed by reference  not everything as you ve said in your question

User · Answer

Just to clarify PHP uses copy on write  so basically everything is a reference until you modify it  but for objects you need to use clone and the   clone   magic method like in the accepted answer

User · Answer

According to previous comment  if you have another object as a member variable  do following   class MyClass     private  someObject     public function   construct          this- gt someObject   new SomeClass           public function   clone          this- gt someObject   clone  this- gt someObject           Now you can do cloning    bar   new MyClass     foo   clone  bar

User · Answer

If you want to fully copy properties of an object in a different instance  you may want to use this technique   Serialize it to JSON and then de-serialize it back to Object

User · Answer

According to previous comment  if you have another object as a member variable  do following   class MyClass     private  someObject     public function   construct          this- gt someObject   new SomeClass           public function   clone          this- gt someObject   clone  this- gt someObject           Now you can do cloning    bar   new MyClass     foo   clone  bar

User · Answer

According to the docs  http   ca3 php net language oop5 cloning     a   clone  b

User · Answer

The answers are commonly found in Java books    cloning  If you don t override clone method  the default behavior is shallow copy  If your objects have only primitive member variables  it s totally ok  But in a typeless language with another object as member variables  it s a headache  serialization deserialization    new object   unserialize serialize  your object    This achieves deep copy with a heavy cost depending on the complexity of the object

User · Answer

This code help clone methods  class Foo       private  run 10      public  foo array 2 array 2 8        public function hoo   return 5         public function   clone              this- gt boo function    this- gt hoo                obj new Foo    news   clone  obj  var dump  news- gt hoo

User · Answer

I was doing some testing and got this        class A     public  property     function set property  obj       obj- gt property    after     var dump  obj       a   new A     a- gt property    before       Creates a new Object from  a  Like  new A      b   new  a     Makes a Copy of var  a  not referenced   c   clone  a   set property  a      object A  1  1      property    gt  string 5   after     var dump  a      Because function set property get by reference    object A  1  1      property    gt  string 5   after    var dump  b      object A  2  1      property    gt  NULL   var dump  c      object A  3  1      property    gt  string 6   before        Now creates a new obj A and passes to the function by clone  will copied   d   new A     d- gt property    before    set property clone  d      A new variable was created from  d  and not made a reference    object A  5  1      property    gt  string 5   after     var dump  d      object A  4  1      property    gt  string 6   before       gt

User · Answer

The answers are commonly found in Java books    cloning  If you don t override clone method  the default behavior is shallow copy  If your objects have only primitive member variables  it s totally ok  But in a typeless language with another object as member variables  it s a headache  serialization deserialization    new object   unserialize serialize  your object    This achieves deep copy with a heavy cost depending on the complexity of the object

User · Answer

According to the docs  http   ca3 php net language oop5 cloning     a   clone  b

User · Answer

The answers are commonly found in Java books    cloning  If you don t override clone method  the default behavior is shallow copy  If your objects have only primitive member variables  it s totally ok  But in a typeless language with another object as member variables  it s a headache  serialization deserialization    new object   unserialize serialize  your object    This achieves deep copy with a heavy cost depending on the complexity of the object

User · Answer

This code help clone methods  class Foo       private  run 10      public  foo array 2 array 2 8        public function hoo   return 5         public function   clone              this- gt boo function    this- gt hoo                obj new Foo    news   clone  obj  var dump  news- gt hoo

User · Answer

I was doing some testing and got this        class A     public  property     function set property  obj       obj- gt property    after     var dump  obj       a   new A     a- gt property    before       Creates a new Object from  a  Like  new A      b   new  a     Makes a Copy of var  a  not referenced   c   clone  a   set property  a      object A  1  1      property    gt  string 5   after     var dump  a      Because function set property get by reference    object A  1  1      property    gt  string 5   after    var dump  b      object A  2  1      property    gt  NULL   var dump  c      object A  3  1      property    gt  string 6   before        Now creates a new obj A and passes to the function by clone  will copied   d   new A     d- gt property    before    set property clone  d      A new variable was created from  d  and not made a reference    object A  5  1      property    gt  string 5   after     var dump  d      object A  4  1      property    gt  string 6   before       gt

User · Answer

In this example we will create iPhone class and make exact copy from it by cloning  class iPhone    public  name  public  email       public function   construct  n   e             this- gt name    n          this- gt email    e              main   new iPhone  Dark    m m com     copy   clone  main       if you want to print both objects  just write this      echo   lt pre gt    print r  main    echo   lt  pre gt    echo   lt pre gt    print r  copy    echo   lt  pre gt

User · Answer

According to previous comment  if you have another object as a member variable  do following   class MyClass     private  someObject     public function   construct          this- gt someObject   new SomeClass           public function   clone          this- gt someObject   clone  this- gt someObject           Now you can do cloning    bar   new MyClass     foo   clone  bar

User · Answer

In this example we will create iPhone class and make exact copy from it by cloning  class iPhone    public  name  public  email       public function   construct  n   e             this- gt name    n          this- gt email    e              main   new iPhone  Dark    m m com     copy   clone  main       if you want to print both objects  just write this      echo   lt pre gt    print r  main    echo   lt  pre gt    echo   lt pre gt    print r  copy    echo   lt  pre gt

User · Answer

Just to clarify PHP uses copy on write  so basically everything is a reference until you modify it  but for objects you need to use clone and the   clone   magic method like in the accepted answer

User · Answer

According to the docs  http   ca3 php net language oop5 cloning     a   clone  b

User · Answer

If you want to fully copy properties of an object in a different instance  you may want to use this technique   Serialize it to JSON and then de-serialize it back to Object

User · Answer

The answers are commonly found in Java books    cloning  If you don t override clone method  the default behavior is shallow copy  If your objects have only primitive member variables  it s totally ok  But in a typeless language with another object as member variables  it s a headache  serialization deserialization    new object   unserialize serialize  your object    This achieves deep copy with a heavy cost depending on the complexity of the object

User · Answer

According to the docs  http   ca3 php net language oop5 cloning     a   clone  b

User · Answer

According to previous comment  if you have another object as a member variable  do following   class MyClass     private  someObject     public function   construct          this- gt someObject   new SomeClass           public function   clone          this- gt someObject   clone  this- gt someObject           Now you can do cloning    bar   new MyClass     foo   clone  bar

[php] How do I create a copy of an object in PHP?

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