The function in_array() returns true if an item exists in an array.
$fruits = ['banana', 'apple'];
$foo = in_array('banana', $fruits);
// $foo value is true
$bar = in_array('orange', $fruits);
// $bar value is falseYou can also use the function array_search() to get the key of a specific item in an array.
$userdb = ['Sandra Shush', 'Stefanie Mcmohn', 'Michael'];
$pos = array_search('Stefanie Mcmohn', $userdb);
if ($pos !== false) {
echo "Stefanie Mcmohn found at $pos";
}In PHP 5.5 and later you can use array_column() in conjunction with array_search().
This is particularly useful for checking if a value exists in an associative array:
$userdb = [
[
"uid" => '100',
"name" => 'Sandra Shush',
"url" => 'urlof100',
],
[
"uid" => '5465',
"name" => 'Stefanie Mcmohn',
"pic_square" => 'urlof100',
],
[
"uid" => '40489',
"name" => 'Michael',
"pic_square" => 'urlof40489',
]
];
$key = array_search(40489, array_column($userdb, 'uid'));