<?php

$value = "en-us,en;q=0.7,ar-iq;q=0.3";

$accepted = array();
if (preg_match_all("/\s*([^,;]+)(?:;\s*q=([\d.]+))?/", $value, $m, PREG_SET_ORDER)) {
	foreach ($m as $lang) {
		$accepted[] = array(
			'lang' => $lang[1],
			'q' => isset($lang[2]) ? (float)$lang[2] : 1
		);
	}
}

usort($accepted, function($l1, $l2) {
	return ceil((float)$l2['q'] - (float)$l1['q']);
});
var_dump($accepted);