includes/ArrayUtils.php

   1 <?php
   2
   3 class ArrayUtils {
   4         /**
   5          * Sort the given array in a pseudo-random order which depends only on the
   6          * given key and each element value. This is typically used for load
   7          * balancing between servers each with a local cache.
   8          *
   9          * Keys are preserved. The input array is modified in place.
  10          *
  11          * Note: Benchmarking on PHP 5.3 and 5.4 indicates that for small
  12          * strings, md5() is only 10% slower than hash('joaat',...) etc.,
  13          * since the function call overhead dominates. So there's not much
  14          * justification for breaking compatibility with installations
  15          * compiled with ./configure --disable-hash.
  16          *
  17          * @param $array The array to sort
  18          * @param $key The string key
  19          * @param $separator A separator used to delimit the array elements and the
  20          *     key. This can be chosen to provide backwards compatibility with
  21          *     various consistent hash implementations that existed before this
  22          *     function was introduced.
  23          */
  24         static function consistentHashSort( &$array, $key, $separator = "\000" ) {
  25                 $hashes = array();
  26                 foreach ( $array as $elt ) {
  27                         $hashes[$elt] = md5( $elt . $separator . $key );
  28                 }
  29                 uasort( $array, function ( $a, $b ) use ( $hashes ) {
  30                         return strcmp( $hashes[$a], $hashes[$b] );
  31                 } );
  32         }
  33 }