Intercepting calls to methods in PHP - php

Question

I have a class with static methods, and I would like to intercept method calls before the methods are called.
So if I call
$model = DataMapper::getById(12345);
then I want some method in DataMapper to be called before this method is called, and then optionally this intercepting method can subsequently call self::getById(12345). Is there a way to do this?
I am implementing Memcache on my server, so that is why I want to intercept method calls. I don't want the static methods to query the database if models are already cached, and I also don't want to have to modify hundreds of different mapper methods, redundantly, to support memcache.
I am running PHP 5.2.6.

Answer 1

This'd do the job:
Triggering __call() in PHP even when method exists
Just declare your static methods as protected so they're inaccessible outside the class and get the __callStatic() magic method to invoke them.
Edit: oops, you'll be needing 5.3 to do it...

Answer 2

This is one example where you might want to consider ditching static methods in favor of polymorphism. If your data-mapper was an interface then you could have two implementations, one for the database and one for memcache:
interface DataMapper {
public function getById($id);
// other data mapper methods
}
class DataMapper_DB implements DataMapper {
public function getById($id) {
// retrieve from db
}
// other methods
}
class DataMapper_Memcache implements DataMapper {
private $db;
public function __construct(DataMapper_DB $db, $host, ...) {
$this->db = $db;
// other set up
}
public function getById($id) {
// if in memcache return that
// else
$record = $this->db->getById($id);
// add record to memcache
return $record
}
//other methods
}

Answer 3

I just came up with a way to intercept method calls in PHP - Check it out.
It's just a basic example, and classes that want to be interceptible have to "opt in" - you can't interfere with the behavior of classes that don't implement the two magic methods.
I don't know if this meets your needs - but this pattern can be implemented without code generation or runtime bytecode hacks, and that's gotta be a plus ;-)

Answer 4

I guess you could have created some magic with runkit, but you would need to compile the extension from cvs, since the latest version does not support 5.2.x
Example:
<?php
/* Orig code */
class DataMapper {
static public function getById($value) {
echo "I'm " . __CLASS__ . "\n";
}
}
/* New Cache Mapper */
class DataMapper_Cache {
static public function getById($value) {
echo "I'm " . __CLASS__ . "\n";
}
}
// Running before rename and adopt
DataMapper::getById(12345);
// Do the renaming and adopt
runkit_method_rename('DataMapper', 'getById', 'getById_old');
runkit_class_adopt('DataMapper','DataMapper_Cache');
// Run the same code..
DataMapper::getById(12345);
?>
Output:
I'm DataMapper
I'm DataMapper_Cache