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14 years ago
I was playing around with these functions and made a class in the process. This will of course be slower than accessing a variable locally, but gives the ability to store variables in a shared environment and gives many running scripts the understanding that it should access them from the shared area. This should also auto destroy the shared memory area once no more scripts have a link to the data (when all scripts use this class).

<?php
class SharedMemory{
    private $nameToKey = array();
    private $key;
    private $id;
    function __construct($key = null){
        if($key === null){
            $tmp = tempnam('/tmp', 'PHP');
            $this->key = ftok($tmp, 'a');
            $this->id = shm_attach($this->key);
            $this->nameToKey[] = '';
            $this->nameToKey[] = '';
            $this->updateMemoryVarList();
            shm_put_var($this->id, 1, 1);
        }else{
            $this->key = $key;
            $this->id = sem_get($this->key);
            $this->refreshMemoryVarList();
            shm_put_var($this->id, 1, shm_get_var($this->id, 1) + 1);
        }
        if(!$this->id)
            die('Unable to create shared memory segment');
    }
    function __sleep(){
        shm_detach($this->id);
    }
    function __destruct(){
        if(shm_get_var($this->id, 1) == 1){
            // I am the last listener so kill shared memory space
            $this->remove();
        }else{
            shm_detach($this->id);
            shm_put_var($this->id, 1, shm_get_var($this->id, 1) - 1);
        }
    }
    function __wakeup(){
        $this->id = sem_get($this->key);
        shm_attach($this->id);
        $this->refreshMemoryVarList();
        shm_put_var($this->id, 1, shm_get_var($this->id, 1) + 1);
    }
    function getKey(){
        return $this->key;
    }
    function remove(){
        shm_remove($this->id);
    }
    function refreshMemoryVarList(){
        $this->nameToKey = shm_get_var($this->id, 0);
    }
    function updateMemoryVarList(){
        shm_put_var($this->id, 0, $this->nameToKey);
    }
    function __get($var){
        if(!in_array($var, $this->nameToKey)){
            $this->refreshMemoryVarList();
        }
        return shm_get_var($this->id, array_search($var, $this->nameToKey));
    }
    function __set($var, $val){
        if(!in_array($var, $this->nameToKey)){
            $this->refreshMemoryVarList();
            $this->nameToKey[] = $var;
            $this->updateMemoryVarList();
        }
        shm_put_var($this->id, array_search($var, $this->nameToKey), $val);
    }
}

// Example
$sharedMem = new SharedMemory();
$pid = pcntl_fork();
if($pid){
    //parent
    sleep(1);
    echo "Parent Says: " . $sharedMem->a . "\n";
    echo "Parent Changed to 0\n";
    $sharedMem->a = 0;
    //Parent just changed it to 0
    echo "Parent Says: " . $sharedMem->a . "\n";
    sleep(2);
    // Parent think's it's 0, but child has changed it to 1
    echo "Parent Says: " . $sharedMem->a . "\n";
}else{
    //child
    $sharedMem->a = 2;
    echo "Child Changed to 2\n";
    // Should be 2 as child just set it to 2
    echo "Child Says: " . $sharedMem->a . "\n";
    sleep(2);
    // Child think's it's 2, but the parent set it to 0.
    echo "Child Says: " . $sharedMem->a . "\n";
    echo "Child Added 1\n";
    $sharedMem->a++;
    echo "Child Says: " . $sharedMem->a . "\n";
}
?>
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