Question

Is something like the following possible in PHP?

$blah = 'foo1';  class foo2 extends $blah {     //... }  class foo1 {     //... } 

This gives an error.

I want to dynamically set $blah so I can extend whatever class I want.

Edit: The reason for wanting to do this because I wanted to use a function out of another class in a related class. In the end it would have been something like:

Final extends foo1 extends foo2 extends foo3 extends foo4 extends parent { ... } 

In the end I decided to instantiate the other class within the class and use it. Not the best options because they both you 2 of the same classes, but this won’t be used that often, so it will work for now.

Answer 1

You’re assuming here php executes top to bottom, but it doesn’t quite work like that:

<?php foo();  # works  function foo(){   print 'bar'; } 

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<?php  foo();  #dies  if( $i == 1 ) {   function foo(){     print 'bar';   } } 

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<?php $i = 1; if( $i == 1 ) {   function foo(){     print 'bar';   } }  foo(); #works 

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Now, although you can conditionally create classes:

<?php  class A { } class B { } if( false ){    class C extends B {      public static function bar(){       print 'baz';      }   } } C::bar(); # dies 

You cant instantiate one at runtime from a variable:

<?php class A { } class B { } $x = 'B';  if( false ){    class C extends $x {      public static function bar(){       print 'baz';      }   } } C::bar(); ---> Parse error: syntax error, unexpected T_VARIABLE, expecting T_STRING in /tmp/eg.php on line 7 

There is a way to do it with Eval, but you really don’t want to go there:

<?php  class A { } class B { } $x = 'B';  if( true ){   $code =<<<EOF   class C extends $x {      public static function bar(){       print 'baz';      }   } EOF;    eval( $code ); } C::bar(); $o = new C;  if ( $o instanceof $x ) {   print 'WIN!\n'; } --->barWIN! 

However, there is a more important question here:

Why the hell would you want to extend a different class at runtime

Anybody using your code will want to hold you down and whip you for that.

( Alternatively, if you’re into whipping, do that eval trick )