How can I check if a function already exists in the SPL stack?

Question

I am trying to use spl_autoload_register and I want to create an if() statement that will check if the class method as already been registered.

For example:

if (spl_autoload_function(array($this, '_loadClass'))
    // Then do nothing
else
    // Then run spl_autoload_register(array($this, '_loadClass));

Is something like the above code/method possible?

Answer 1

I am trying to do an autoloader and I want to create an if statement that will check if the class method as already been registered.

You shouldn't. There is no need to do the if statement; spl_autoload_register will just ignore a second call with the same arguments:

<?php

$foo = function( $class ) {
    return false;
};

spl_autoload_register( $foo );
var_dump( spl_autoload_functions( ) );

spl_autoload_register( $foo );
var_dump( spl_autoload_functions( ) );

The output shows that although we called spl_autoload_register twice, there is still just one autoloader;

array(1) {
  [0]=>
  object(Closure)#1 (1) {
    ["parameter"]=>
    array(1) {
      ["$class"]=>
      string(10) "<required>"
    }
  }
}
array(1) {
  [0]=>
  object(Closure)#1 (1) {
    ["parameter"]=>
    array(1) {
      ["$class"]=>
      string(10) "<required>"
    }
  }
}

If you want to make sure a class doesn't register itself twice, you can of course set that in some kind of static member;

<?php
class Foo {
    protected static $registered = false;

    public function register( ) {
        if( self::$registered !== false ) {
            return;
        }
        echo "spl_autoload_register( \$this, '_loadClass' );\n";
        self::$registered = true;
    }
}

$foo = new Foo( );
$foo->register( );

$bar = new Foo( );
$bar->register( );

The output is obviously one line:

spl_autoload_register( $this, '_loadClass' );

That said, why are you writing your own autoloader? There are numerous out there already, it's hard to believe that none of them fit your requirements.

Answer 2

Disclaimer: I'm not fully confident I understood your question, but I'm confident enough I thought I'd try to answer.

---

There is no spl_* function to do this. The closest you get is spl_autoload_functions() which returns the functions that the spl uses to load, not the functions being loaded.

Solution:

Write your own loader that logs when a function/class has been loaded and register it with spl_autoload_register.

---

To answer comment: If you have a class that loads functions, have it append to an internal array of classes it has already loaded.

class Autoloader {

    protected $loaded = array();

    function autoload($class) {
        // find class location
        // if it is found:
        // include class
        $this->loaded[] = $class;
    }

    function hasLoaded($class) {
        return in_array($class, $this->loaded);
    }

}

$autoloader = new Autoloader();
spl_autoload_register(array($autloader, 'autoload'));

If you don't care to know if it was loaded by the autoloader, you can simply check for existence using class_exists.