Probably, one of the most used functions with arrays is in_array. This function takes two values, the value that you want to search for and the array. The function returns true if the value is in the array and false otherwise. This is very useful, because a lot of times what you want to know from a list or a map is if it contains an element, rather than knowing that it does or its location.

Even more useful sometimes is array_search. This function works in the same way except that instead of returning a Boolean, it returns the key where the value is found, or false otherwise. Let's see both functions:

<?php
$names = ['Harry', 'Ron', 'Hermione'];
$containsHermione = in_array('Hermione', $names);
var_dump($containsHermione); // true
$containsSnape = in_array('Snape', $names);
var_dump($containsSnape); // false
$wheresRon = array_search('Ron', $names);
var_dump($wheresRon); // 1
$wheresVoldemort = array_search('Voldemort', $names);
var_dump($wheresVoldemort); // false