airpc/examples/test.php

<?php
$units = array();
for($i=0;$i<1000000;$i++){
    $units[] = uniqid();
    echo $units[$i].PHP_EOL;
}
$values  = array_count_values($units);
$duplicates = [];
foreach($values as $k=>$v){
    if($v>1){
        $duplicates[$k]=$v;
    }
}
echo '<pre>';
print_r($duplicates);
echo '</pre>';
?>