php生成不重复随机数、数组的4种方法分享

echo 'max random num: '.RANDOM_MAX, ' ;result count:'.COUNT, '<br/>';

invoke_entry('rand1');
invoke_entry('rand2');
invoke_entry('rand3');
invoke_entry('rand4');

function invoke_entry($func_name) {
 $time = new time();
 $time->time_start();
 call_user_func($func_name);
 echo $func_name.' time spend: ', $time->time_spend();
 echo '<br/>';
}
function rand1() {
 $numbers = range (1, RANDOM_MAX);
 shuffle($numbers); //随机打乱数组
 $result = array_slice($numbers, 1, COUNT);
 return $result;
}
function rand2() {
 $result = array();
 while(count($result)< COUNT) {
  $result[] = mt_rand(1, RANDOM_MAX); //mt_rand()是比rand()更好更快的随机函数
  $result = array_unique($result); //删除数组中重复的元素
 }
 return $result;
}
function rand3() {
 $result = array();  
 while(count($result) < COUNT) {
  $_tmp = mt_rand(1, RANDOM_MAX);
  if(!in_array($_tmp, $result)) { //当数组中不存在相同的元素时，才允许插入
   $result[] = $_tmp;
  }
 }  
 return $result;
}
function rand4() {
 $result = array();
 while (count($result) < COUNT) {
  $result[] = mt_rand(1, RANDOM_MAX);
  $result = array_flip(array_flip($result)); //array_flip将数组的key和value交换
 }
 return $result;
}
class time {
 private $_start;
 
 public function time_start() {
  $this->_start = $this->microtime_float();
 }
 public function time_spend() {
  return $this->microtime_float() - $this->_start;
 }
 private function microtime_float() {
  list($usec, $sec) = explode(" ", microtime());
  return ((float)$usec + (float)$sec);
 }
}

?>