php get keys of duplicate values in array
<?php
/**
Examples of these functions:
array_unique,
array_diff_assoc,
array_diff,
array_keys,
array_intersect
Examle with an array:
*/
$array = array('a', 'a', 'b', 'c', 'd');
// Unique values
$unique = array_unique($array);
// Duplicates
$duplicates = array_diff_assoc($array, $unique);
// Unique values
$result = array_diff($unique, $duplicates);
// Get the unique keys
$unique_keys = array_keys($result);
// Get duplicate keys
$duplicate_keys = array_keys(array_intersect($array, $duplicates));