function RandomSplit($min, $max, $str){
  $a = array();
  while ($str != ''){
    $p = rand($min, $max);
    $p = ($p > strlen($str)) ? strlen($str) : $p;
    $buffer = substr($str, 0, $p);
    $str = substr($str, $p, strlen($str)-$p);
    $a[] = $buffer;
  }
  return $a;
}
//范例：
/*
** Example:
*/
$test_string = 'This is a example to test the RandomSplit function.';
print_r(RandomSplit(1, 7, $test_string));
/*
Outputs something like this
(Array items are 1 to 7 characters long): 
Array
(
  [0] => This
  [1] => is
  [2] => a exam
  [3] => ple to
  [4] => test t
  [5] => he
  [6] => 
  [7] => ran
  [8] => d_spl
  [9] => it f
  [10] => un
  [11] => ction.
)
*/