php;"> $num = 0;   $array = array(1, 2, 3, 4, 5, 6, 7, 8, 9);   $arr = array();   $g = 5;   $tag = true;   while ($tag) {     $count = count($array);     $t = rand(0, 1);     if ($t == 1) {       $arr[] = $array[$num];       unset($array[$num]);     }     $num ++;     if (count($arr) == $g) {       $tag = false;     }     if ($num == $count) {       $num = 0;  //循環     }   }  var_dump($arr); 

  function swap(&$a, &$b)   {     $temp = $b;     $b = $a;     $a = $temp;   }         $result = array();   $src = array();   for($i = 0 ; $i < 40 ; $i++)   {     $src[] = $i + 1;   }   $arr_len = count($src);   $count = 20;   $index = 0;   while($index < $count)   {     $random = rand(0, $arr_len - $index - 1);     $result[] = $src[$random];     swap($src[$random] , $src[$arr_len - $index - 1]);     $index += 1;   }         print_r(json_encode($result));   print_r(json_encode($src));