<?php
$arr1 = array(array("size"=>"M","colour" => "black"),array("size"=>"S","colour" => "blue"));
$arr2 = array("size"=>"M","colour" => "black");
print_r($arr1);
print_r($arr2);

foreach($arr1 as $marray)
{
  if($marray['size'] == $arr2['size'] && $marray['colour'] == $arr2['colour'])
  {
  echo "match found";
  }
}
?>

Array
(
    [0] => Array
        (
            [size] => M
            [colour] => black
        )

    [1] => Array
        (
            [size] => S
            [colour] => blue
        )

)
Array
(
    [size] => M
    [colour] => black
)
match found