php 求质素(素数) 的实现代码

复制代码 代码如下:

  <?php

  class timer

  {

  var $time_start;

  var $time_end;

  function __construct()

  {

  $this->time_start = 0;

  $this->time_end = 0;

  }

  function timer()

  {

  $this->__construct();

  }

  function start()

  {

  list($usec,$sec) = explode(" ",microtime());

  $this->time_start = (float)$usec + (float)$sec;

  }

  function stop()

  {

  list($usec,$sec) = explode(" ",microtime());

  $this->time_end = (float)$usec + (float)$sec;

  }

  function show($output = false)

  {

  $total = $this->time_end - $this->time_start;

  if ($output) {

  echo $total," sec";

  return true;

  }

  return $total." sec";

  }

  }

  ?>

  <?php

  echo 'check prime<br/>';

  function IsPrime($i)

  {

  if($i<2)

  {

  return false;

  }

  //var $iterator;

  for($iterator = 2 ; $iterator <= sqrt($i) ; $iterator++)

  {

  if($i % $iterator==0)

  {

  return false;

  }

  }

  return true;

  }

  $sw=new timer();

  $sw->start();

  for($j=1;$j<100;$j++)

  {

  if(IsPrime($j))

  {

  echo 'true<br/>';

  }

  else

  {

  echo 'false<br/>';

  }

  }

  $sw->stop();

  $sw->show(true);

  ?>