Notify stock availability for a specific size

EastBay Size Notification

<?php
    function checkStock($url,$sku,$size, $nick = null){
        $content = file_get_contents($url);
        $find = $sku.'":["<span class';
        $start = strpos($content,$find);
        $end   = strpos($content,"]]",$start);
        
        $substr = substr($content,$start,$end-$start);
    
        if (strpos($substr,$size) !== false){
            mail("alvin@alvinnguyen.net","$nick $size Available",$url);
        }
    }

    checkStock("http://www.eastbay.com/product/model:214312/sku:42198001/nike-free-5.0-2014-mens/black/grey/","42198001","08.0","Nike Free Men");
?>