<?php
function parseCacheControl($header)
{
    $cacheControl = array();
    preg_match_all('#([a-zA-Z][a-zA-Z_-]*)\s*(?:=(?:"([^"]*)"|([^ \t",;]*)))?#', $header, $matches, PREG_SET_ORDER);
    foreach ($matches as $match) {
        $cacheControl[strtolower($match[1])] = isset($match[2]) && $match[2] ? $match[2] : (isset($match[3]) ? $match[3] : true);
    }

    return $cacheControl;
}

var_dump(parseCacheControl('no-store& private=test, no-cache="a,b,c"'));

$start = microtime(true);
for ($i=0; $i<10000; $i++) {
    parseCacheControl('no-store, private=test, no-cache="a,b,c"');
}
var_dump(microtime(true) - $start);