Efficient use of arrays

[Matt_T_hat]

Now the fastest way to do this would be with an SQL SELECT statment but as this is not possible I need to have reasonable speed even with big arrays

Belo are my functions which are logically simple. However is there a way of getting the same results but less processor cycles?

    // returns array
    function all_x_where_y_equals($x, $y, $val, $from){
        $new = array();
        foreach ($from as $fr){
            if ($fr[$y] == $val){
                $new[] = $fr[$x]
            }
        }
        return $new;
    }
    
    // returns array
    function all_keys_where_y_equals($y, $val, $from){
        $new = array();
        foreach ($from as $k => $fr){
            if ($fr[$y] == $val){
                $new[] = $k
            }
        }
        return $new;
    }