PHP array_unique

 1 <?php
 2 $array1 = range(1,500000,3);
 3 $array2 = range(1,500000,4);
 4 $arr = array_merge($array1,$array2);
 5 echo ‘count :‘ .count($arr) . "\n";
 6 
 7 $begin_time = microtime(true);
 8 array_keys(array_flip($arr));
 9 $end_time = microtime(true);
10 print_r($end_time - $begin_time);
11 
12 echo "\n";
13 $begin_time = microtime(true);
14 array_flip(array_flip($arr));
15 $end_time = microtime(true);
16 print_r($end_time - $begin_time);
17 
18 echo "\n";
19 $begin_time = microtime(true);
20 array_unique($arr);
21 $end_time = microtime(true);
22 print_r($end_time - $begin_time);