ArrayUtils.php

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<?php

class ArrayUtils {
        public static function consistentHashSort( &$array, $key, $separator = "\000" ) {
                $hashes = array();
                foreach ( $array as $elt ) {
                        $hashes[$elt] = md5( $elt . $separator . $key );
                }
                uasort( $array, function ( $a, $b ) use ( $hashes ) {
                        return strcmp( $hashes[$a], $hashes[$b] );
                } );
        }

        public static function pickRandom( $weights ){
                if ( !is_array( $weights ) || count( $weights ) == 0 ) {
                        return false;
                }

                $sum = array_sum( $weights );
                if ( $sum == 0 ) {
                        # No loads on any of them
                        # In previous versions, this triggered an unweighted random selection,
                        # but this feature has been removed as of April 2006 to allow for strict
                        # separation of query groups.
                        return false;
                }
                $max = mt_getrandmax();
                $rand = mt_rand( 0, $max ) / $max * $sum;

                $sum = 0;
                foreach ( $weights as $i => $w ) {
                        $sum += $w;
                        # Do not return keys if they have 0 weight.
                        # Note that the "all 0 weight" case is handed above
                        if ( $w > 0 && $sum >= $rand ) {
                                break;
                        }
                }
                return $i;
        }
}