TempStreamIterator.php

<?php
/**
 * TempStreamIterator.php
 * 
 * Caches an iterable into a temporary stream, memory or file backed.
 * Result is rewindable.
 * 
 */
 
class TempStreamIterator implements \Iterator
{
    protected $fp;
    
    protected $key, $val;
    
    public function __construct($t, $memory = 10) {
        $memory = $memory * 1024 * 1024;
        $this->fp = fopen("php://temp/maxmemory:$memory", "r+");
        foreach($t as $k => $v) {
            $o = serialize([$k, $v]);
            fputs($this->fp, "$o\n");
        }
    }
    
    public function __destruct() {
        fclose($this->fp);
    }
    
    public function current() {
        return $this->val;
    }
    
    public function key() {
        return $this->key;
    }

    public function next() {
        list($this->key, $this->val) = unserialize(trim(fgets($this->fp)));
    }
    
    public function rewind() {
        rewind($this->fp);
        $this->next();
    }

    public function valid() {
        return ($this->key !== null);
    }
    
}