$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) { 
      $num = 0;  //循环 
    } 
  } 
 var_dump($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));