How to find duplicate values in an array

Short answer

Count how often each value occurs and keep those above one:

<?php
 
$emails = ['a@x.com', 'b@x.com', 'a@x.com', 'c@x.com', 'b@x.com'];
 
$duplicates = array_keys(array_filter(array_count_values($emails), fn ($count) => $count > 1));
 
echo implode(', ', $duplicates);

Output:

a@x.com, b@x.com

Are there any repeats at all

Compare the length of the array with its length without repeats:

<?php
 
$ids = [3, 7, 3, 9];
 
var_dump(count($ids) !== count(array_unique($ids)));

Output:

bool(true)

Thanks for reading!

Short answer

Are there any repeats at all

Functions used in this recipe

Thanks for reading!