How to resolve must be an instance of string string given prior to PHP 7

Question

Here is my code   function phpwtf string  s        echo   s n     phpwtf  Type hinting is da bomb      Which results in this error      Catchable fatal error  Argument 1 passed to phpwtf   must be an instance of string  string given   It s more than a little Orwellian to see PHP recognize and reject the desired type in the same breath  There are five lights  damn it   What is the equivalent of type hinting for strings in PHP  Bonus consideration to the answer that explains exactly what is going on here

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From PHP s manual    Type Hints can only be of the object and array  since PHP 5 1  type  Traditional type hinting with int and string isn t supported   So you have it  The error message is not really helpful  I give you that though     2017 Edit    PHP7 introduced more function data type declarations  and the aforementioned link has been moved to Function arguments   Type declarations  From that page    Valid types   Class interface name   The parameter must be an instanceof the given class or interface name   since PHP 5 0 0  self   The parameter must be an instanceof the same class as the one the method is defined on  This can only be used on class and instance methods   since PHP 5 0 0  array   The parameter must be an array   since PHP 5 1 0  callable   The parameter must be a valid callable      since PHP 5 4 0  bool   The parameter must be a boolean value   since PHP 7 0 0  float   The parameter must be a floating point number   since PHP 7 0 0  int   The parameter must be an integer   since PHP 7 0 0  string   The parameter must be a string   since PHP 7 0 0  iterable   The parameter must be either an array or an instanceof Traversable   since PHP 7 1 0    Warning Aliases for the above scalar types are not supported  Instead  they are treated as class or interface names  For example  using boolean as a parameter or return type will require an argument or return value that is an instanceof the class or interface boolean  rather than of type bool     lt  php   function test boolean  param       test true     gt     The above example will output     Fatal error  Uncaught TypeError  Argument 1 passed to test   must be an instance of boolean  boolean given  called in - on line 1 and defined in - 1   The last warning is actually significant to understand the error  quot Argument must of type string  string given quot   since mostly only class interface names are allowed as argument type  PHP tries to locate a class name  quot string quot   but can t find any because it is a primitive type  thus fail with this awkward error

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I think typecasting on php on inside block  String on PHP is not object as I know    lt  php function phpwtf  s         s    string   s      echo   s n     phpwtf  Type hinting is da bomb

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I got this error when invoking a function from a Laravel Controller to a PHP file   After a couple of hours  I found the problem  I was using  this from within a static function

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Maybe not safe and pretty but if you must   class string       private  Text      public function   construct  value                 this- gt Text    value             public function   toString                 return  this- gt Text           function Test123 string  s        echo  s     Test123 new string  Testing

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As others have already said  type hinting currently only works for object types  But I think the particular error you ve triggered might be in preparation of the upcoming string type SplString   In theory it behaves like a string  but since it is an object would pass the object type verification  Unfortunately it s not yet in PHP 5 3  might come in 5 4  so haven t tested this

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Prior to PHP 7 type hinting can only be used to force the types of objects and arrays  Scalar types are not type-hintable  In this case an object of the class string is expected  but you re giving it a  scalar  string  The error message may be funny  but it s not supposed to work to begin with  Given the dynamic typing system  this actually makes some sort of perverted sense   You can only manually  type hint  scalar types   function foo  string        if   is string  string             trigger error  No  you fool             return

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As of PHP 7 0 type declarations allow scalar types  so these types are now available  self  array  callable  bool  float  int  string  The first three were available in PHP 5  but the last four are new in PHP 7  If you use anything else  e g  integer or boolean  that will be interpreted as a class name   See the PHP manual for more information

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PHP allows  hinting  where you supply a class to specify an object   According to the PHP manual   Type Hints can only be of the object and array  since PHP 5 1  type  Traditional type hinting with int and string isn t supported    The error is confusing because of your choice of  string  - put  myClass  in its place and the error will read differently   Argument 1 passed to phpwtf   must be an instance of myClass  string given

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originally posted by leepowers in his question  The error message is confusing for one big reason  Primitive type names are not reserved in PHP The following are all valid class declarations  class string     class int     class float     class double      My mistake was in thinking that the error message was referring solely to the string primitive type - the word  instance  should have given me pause  An example to illustrate further  class string      n   1234   s1    string  n   s2   new string     a   array  no    yes    printf  quot   s1 - primitive string   s - string instance   s n quot            a is string  s1     a is a  s1   string      printf  quot   s2 - primitive string   s - string instance   s n quot            a is string  s2     a is a  s2   string       Output    s1 - primitive string  yes - string instance  no  s2 - primitive string  no - string instance  yes  In PHP it s possible for a string to be a string except when it s actually a string  As with any language that uses implicit type conversion  context is everything

[php] How to resolve "must be an instance of string, string given" prior to PHP 7?

2017 Edit

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