php使用令牌Token防止表单重复提交

php使用令牌Token防止表单重复提交原理在于生成一个随机字符串放在session里，提交表单后来验证这个字符串，可以做到防止他人自己写form来欺骗提交，重复提交或者双击提交。

<?php
/*
* PHP使用token防止表单重复提交
* 此处理方法纯粹是为了给初学者参考
*/
session_start();
function set_token() {
  $_SESSION[\'token\'] = md5(microtime(true));
}
function valid_token() {
  $return = $_REQUEST[\'token\'] === $_SESSION[\'token\'] ? true : false;
  set_token();
  return $return;
}
//如果token为空则生成一个token (作者：码农教程  http://www.manongjc.com )
if(!isset($_SESSION[\'token\']) || $_SESSION[\'token\']==\'\') {
  set_token();
}
if(isset($_POST[\'test\'])){
  if(!valid_token()){
    echo \"token error\";
  }else{
    echo \'成功提交，Value:\'.$_POST[\'test\'];
  }
}
?>
<form method=\"post\" action=\"\">
  <input type=\"hidden\" name=\"token\" value=\"<?php echo $_SESSION[\'token\']?>\">
  <input type=\"text\" name=\"test\" value=\"Default\">
  <input type=\"submit\" value=\"提交\" />
</form>

上面的比较简单一点的方法，下面的代码更加安全一点。

Token.php

<?php
function getToken($len = 32, $md5 = true) {
  # Seed random number generator
  # Only needed for PHP versions prior to 4.2
  mt_srand((double) microtime() * 1000000);
  # Array of characters, adjust as desired
  $chars = array (\'Q\',\'@\',\'8\',\'y\',\'%\',\'^\',\'5\',\'Z\',\'(\',\'G\',\'_\',\'O\',\'`\',\'S\',\'-\',\'N\',\'<\',\'D\',\'{\',\'}\',\'[\',\']\', \'h\',\';\',\'W\', \'.\',\'/\',\'|\',\':\', \'1\',\'E\',\'L\',\'4\',\'&\',\'6\',\'7\',\'#\',\'9\',\'a\',\'A\',\'b\',\'B\',\'~\', \'C\',\'d\',\'>\',\'e\',\'2\',\'f\',\'P\',\'g\',\')\',\'?\',\'H\',\'i\',\'X\',\'U\',\'J\',\'k\',\'r\',\'l\',\'3\',\'t\');
  # Array indice friendly number of chars;
  $numChars = count($chars) - 1;
  $token = \'\';
  # Create random token(作者：码农教程  http://www.manongjc.com/article/1549.html )
  for ($i = 0; $i < $len; $i++)
    $token .= $chars[mt_rand(0, $numChars)];
  # Should token be run through md5?
  if ($md5) {
    # Number of 32 char chunks
    $chunks = ceil(strlen($token) / 32);
    $md5token = \'\';
    # Run each chunk through md5
    for ($i = 1; $i <= $chunks; $i++)
      $md5token .= md5(substr($token, $i * 32 - 32, 32));
    # Trim the token
    $token = substr($md5token, 0, $len);
  }
  return $token;
}
?>

form.php

<?php
include_once(\"token.php\");
$token = getToken();
session_start();
$_SESSION[\'token\'] = $token;
?>
<form action=\"action.php\" method=\"post\"
<input type=\"hidden\" name=\"token\" value=\"<?=$token?>\" />
<!-- 其他input submit之类的 -->
</form>

action.php

<?php
session_start();
if($_POST[\'token\'] == $_SESSION[\'token\']){
  unset($_SESSION[\'token\']);
  echo \"这是一个正常的提交请求\";
}else{
  echo \"这是一个非法的提交请求\";
}
?>