How can I check if an array contains a specific value in php?

Use the in_array() function.

$array = array('kitchen', 'bedroom', 'living_room', 'dining_room');

if (in_array('kitchen', $array)) {
    echo 'this array contains kitchen';
}

// Once upon a time there was a farmer

// He had multiple haystacks
$haystackOne = range(1, 10);
$haystackTwo = range(11, 20);
$haystackThree = range(21, 30);

// In one of these haystacks he lost a needle
$needle = rand(1, 30);

// He wanted to know in what haystack his needle was
// And so he programmed...
if (in_array($needle, $haystackOne)) {
    echo "The needle is in haystack one";
} elseif (in_array($needle, $haystackTwo)) {
    echo "The needle is in haystack two";
} elseif (in_array($needle, $haystackThree)) {
    echo "The needle is in haystack three";
}

// The farmer now knew where to find his needle
// And he lived happily ever after

See in_array

<?php
    $arr = array(0 => "kitchen", 1 => "bedroom", 2 => "living_room", 3 => "dining_room");    
    if (in_array("kitchen", $arr))
    {
        echo sprintf("'kitchen' is in '%s'", implode(', ', $arr));
    }
?>