Is it possible to overwrite a function in PHP

Question

Can you declare a function like this...

function ihatefooexamples(){
  return "boo-foo!";
};

And then redeclare it somewhat like this...

if ($_GET['foolevel'] == 10){
  function ihatefooexamples(){
    return "really boo-foo";
  };
};

Is it possible to overwrite a function that way?

Any way?

Answer 1

No this will be a problem. PHP Variable Functions

Answer 2

I'm afraid there's no way to do that.

Answer 3

Have a look at override_function to override the functions.

override_function — Overrides built-in functions

Example:

override_function('test', '$a,$b', 'echo "DOING TEST"; return $a * $b;');

Answer 4

short answer is no, you can't overwrite a function once its in the PHP function scope.

your best of using anonymous functions like so

$ihatefooexamples = function()
{
  return "boo-foo!";
}

//...
unset($ihatefooexamples);
$ihatefooexamples = function()
{
   return "really boo-foo";
}

http://php.net/manual/en/functions.anonymous.php

Answer 5

Are you trying to override a simple function or would you be able to achieve what you want through the use of classes and extending them with override functions?

A bit more background in what you are trying to do would help.

Answer 6

You could use the PECL extension

• runkit_function_redefine — Replace a function definition with a new implementation

but that is bad practise in my opinion. You are using functions, but check out the Decorator design pattern. Can borrow the basic idea from it.

Answer 7

I would include all functions of one case in an include file, and the others in another include.

For instance simple.inc would contain function boofoo() { simple } and really.inc would contain function boofoo() { really }

It helps the readability / maintenance of your program, having all functions of the same kind in the same inc.

Then at the top of your main module

  if ($_GET['foolevel'] == 10) {
    include "really.inc";
  }
  else {
    include "simple.inc";
  }

Answer 8

You cannot redeclare any functions in PHP. You can, however, override them. Check out overriding functions as well as renaming functions in order to save the function you're overriding if you want.

So, keep in mind that when you override a function, you lose it. You may want to consider keeping it, but in a different name. Just saying.

Also, if these are functions in classes that you're wanting to override, you would just need to create a subclass and redeclare the function in your class without having to do rename_function and override_function.

Example:

rename_function('mysql_connect', 'original_mysql_connect' );
override_function('mysql_connect', '$a,$b', 'echo "DOING MY FUNCTION INSTEAD"; return $a * $b;');

Answer 9

This is where you should take advantage of OOP, specifically polymorphism.

interface Fooable
{
  public function ihatefooexamples();
}

class Foo implements Fooable
{
  public function ihatefooexamples()
  {
    return "boo-foo!";
  }
}

class FooBar implements Fooable
{
  public function ihatefooexamples()
  {
    return "really boo-foo";
  }
}

$foo = new Foo();

if ( 10 == $_GET['foolevel'] )
{
  $foo = new FooBar();
}

echo $foo->ihatefooexamples();