<?php

function check_keys_exists($keys_str = "", $arr = array()){
	$return = false;
	if($keys_str != "" and !empty($arr)){
		$keys = explode(',', $keys_str);
		if(!empty($keys)){
			foreach($keys as $key){
				$return = array_key_exists($key, $arr);
				if($return == false){
					break;
				}
			}
		}
	}
	return $return;
}

//run demo
$key = 'a,b,c';
$array = array('a'=>'aaaa','b'=>'ccc','c'=>'eeeee');

var_dump( check_keys_exists($key, $array));