mysqli_real_escape_string foreach function db_array_update

Someone wrote a PHP program many times ago for me, and now I got this error when I run the code :

mysqli_real_escape_string() expects parameter 2 to be string, array given in....

I cannot fix this here is the code :

function db_array_update($table, $a, $where) 
{    
    $q = "update $table set ";
    $b = NULL;  

    foreach($a as $key => $value)   
    {   
        if (is_int($key))
            continue;   

        $con = mysqli_connect("localhost", MYSQLUSER , MYSQLPASS, MYSQLDB);
        $b[] = "$key='".mysqli_real_escape_string($con, $value)."'";        
    }

    $q .= implode(",", $b);
    $q .= " where ".$where;

    db_query($q);

}

and I use it like this :

db_array_update("all_data",array('last_fetched' =>date("Y/m/d H:i:s"),'name'=>$name, 'creation'=>$creat, 'expiration' =>$expire,"id=".$res['id']);

Can someone help me how should I fix this ? Tried many things but not work...