PHP自动给URl添加http://前缀

function fix_url($url, $def=false, $prefix=false) {
	$url = trim($url);
	if (empty($url)){
		return $def;
	}

	if ( count(explode('://',$url))>1 ){
		return $url;
	}else{
		return $prefix===false ? 'http://'.$url : $prefix.$url;
	}
}