Redefine Built in PHP Functions

Redefine Built in PHP Functions

runkit_function_redefine — Replace a function definition with a new implementation

Note: By default, only userspace functions may be removed, renamed, or
modified. In order to override
internal functions, you must enable
the runkit.internal_override setting
in php.ini.

Redefining PHP function?

Nope, that throws an error:

Fatal error: Cannot redeclare foo()

The runkit provides options, including runkit_function_rename() and runkit_function_redefine().

How to override built-in PHP function(s)?

I think it could be done like so:

//First rename existing function
rename_function('strlen', 'new_strlen');
//Override function with another
override_function('strlen', '$string', 'return override_strlen($string);');

//Create the other function
function override_strlen($string){
        return new_strlen($string);  
}

found it here

Notice that every host must have http://php.net/manual/en/book.apd.php installed on the server.

Edit

Another way is to use namespaces

<?php
    namespace mysql2pdo;
    use PDO;
    function mysql_connect() {
       return new PDO();
    }
    echo mysql_connect(); // Causes error because we don't have the parameters
?>

Test it here

PHP - runkit redefine method

{... removed as not necessary ...}

==== EDIT =====

[For the new problem, what you need is this]

<?
class start {
   function __construct() {
       $this->options = array();
   }

   public function process() {
       // some code here
       $this->file_not_exists();
   }

   public function file_not_exists() {
       $this->options['page'] = 222;
   }

   public function redefine($what, $code) {
       runkit_method_redefine(get_class($this), 
       $what, 
       '', 
       'call_user_func(array($this,' .$code. '),$this);', 
       RUNKIT_ACC_PUBLIC);
   }

   public function my_func($someobj)
   {
        print_r($someobj);
   }
}


$start = new start();
$start->redefine('file_not_exists', 'my_func');

$start->process();

?>

PHP - override existing function

Only if you use something like APD that extends the zend engine to allow for that:

Intro

Override Method Docs

Note: Runkit seems like a better option than APD since it's more specific to this purpose and would allow you to keep the original method intact at a different address.

Redefine core function in another namespace

You cannot do this for echo, because it's not actually a function. echo is a "language construct" and a reserved word. You cannot name a function echo.

For built-in functions (that are actually functions) however, what you have is right. For example:

namespace test;
function print_r($yo) {
  \print_r('--' . $yo);
}
print_r('lol');

Redefine Class Methods or Class

It's called monkey patching. But, PHP doesn't have native support for it.

Though, as others have also pointed out, the runkit library is available for adding support to the language and is the successor to classkit. And, though it seemed to have been abandoned by its creator (having stated that it wasn't compatible with PHP 5.2 and later), the project does now appear to have a new home and maintainer.

I still can't say I'm a fan of its approach. Making modifications by evaluating strings of code has always seemed to me to be potentially hazardous and difficult to debug.

Still, runkit_method_redefine appears to be what you're looking for, and an example of its use can be found in /tests/runkit_method_redefine.phpt in the repository:

runkit_method_redefine('third_party_library', 'buggy_function', '',
    'return \'good result\''
);

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