//array_search
$result = array_search("apple", $fruit_array); // return index or false
//in_array
$result = in_array("apple", $fruit_array); // return true or false
array_search ( mixed $needle , array $haystack , bool $strict = false ) : int|string|false
<?php
$array = array(0 => 'blue', 1 => 'red', 2 => 'green', 3 => 'red');
$key = array_search('green', $array); // $key = 2;
$key = array_search('red', $array); // $key = 1;
?>
$userdb = array(
array(
'uid' => '100',
'name' => 'Sandra Shush',
'pic_square' => 'urlof100'
),
array(
'uid' => '5465',
'name' => 'Stefanie Mcmohn',
'pic_square' => 'urlof100'
),
array(
'uid' => '40489',
'name' => 'Michael',
'pic_square' => 'urlof40489'
)
);