怎么样通过php从一个数组中随机的取出若干个不同数？

 $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));