Summary of filtering special dangerous characters in php

We may encounter some security issues when submitting forms or obtaining values from URLs on the website. Below I have summarized some commonly used solutions to filter some dangerous special characters. I hope this tutorial will be helpful to you.

Generally, for the characters passed in, PHP can use the addslashes function to process them (only get_magic_quotes_gpc() is false, otherwise they will be escaped again!), so that a certain degree of security requirements can be achieved
Like this

The code is as follows

Copy code

代码如下	复制代码
if (!get_magic_quotes_gpc()) { add_slashes($_GET); add_slashes($_POST); add_slashes($_COOKIE); } function add_slashes($string) { if (is_array($string)) { foreach ($string as $key => $value) { $string[$key] = add_slashes($value); } } else { $string = addslashes($string); } return $string; }

if (!get_magic_quotes_gpc()) { add_slashes($_GET); add_slashes($_POST); add_slashes($_COOKIE); } function add_slashes($string) { If (is_array($string)) { foreach ($string as $key => $value) { $string[$key] = add_slashes($value); } else { $string = addslashes($string); } Return $string; }

但是还可以更进一步进行重新编码，解码，如下：

代码如下

复制代码

//编码

function htmlencode($str) {
      if(empty($str)) return;
      if($str=="") return $str;
      $str=trim($str);
      $str=str_replace("&","&",$str);
      $str=str_replace(">",">",$str);
      $str=str_replace("<","<",$str);
      $str=str_replace(chr(32)," ",$str);
      $str=str_replace(chr(9)," ",$str);
      $str=str_replace(chr(34),"&",$str);
      $str=str_replace(chr(39),"'",$str);
      $str=str_replace(chr(13),"<br />",$str);
      $str=str_replace("'","''",$str);
      $str=str_replace("select","select",$str);
      $str=str_replace("join","join",$str);
      $str=str_replace("union","union",$str);
      $str=str_replace("where","where",$str);
      $str=str_replace("insert","insert",$str);
      $str=str_replace("delete","delete",$str);
      $str=str_replace("update","update",$str);
      $str=str_replace("like","like",$str);
      $str=str_replace("drop","drop",$str);
      $str=str_replace("create","create",$str);
      $str=str_replace("modify","modify",$str);
      $str=str_replace("rename","rename",$str);
      $str=str_replace("alter","alter",$str);
      $str=str_replace("cast","cas",$str);
      return $str;
}

这样就能更放心的对外来数据进行入库处理了，但是从数据库取出来，在前台显示的时候，必须重新解码一下：

代码如下

复制代码

//解码

function htmldecode($str) {
      if(empty($str)) return;
      if($str=="") return $str;
      $str=str_replace("select","select",$str);
      $str=str_replace("join","join",$str);
      $str=str_replace("union","union",$str);
      $str=str_replace("where","where",$str);
      $str=str_replace("insert","insert",$str);
      $str=str_replace("delete","delete",$str);
      $str=str_replace("update","update",$str);
      $str=str_replace("like","like",$str);
      $str=str_replace("drop","drop",$str);
      $str=str_replace("create","create",$str);
      $str=str_replace("modify","modify",$str);
      $str=str_replace("rename","rename",$str);
      $str=str_replace("alter","alter",$str);
      $str=str_replace("cas","cast",$str);
      $str=str_replace("&","&",$str);
      $str=str_replace(">",">",$str);
      $str=str_replace("<","<",$str);
      $str=str_replace(" ",chr(32),$str);
      $str=str_replace(" ",chr(9),$str);
      $str=str_replace("&",chr(34),$str);
      $str=str_replace("'",chr(39),$str);
      $str=str_replace("<br />",chr(13),$str);
      $str=str_replace("''","'",$str);
      return $str;
}

虽然多了一步编码，解码的过程，但是安全方面，会更进一步，要如何做，自己取舍吧。

再附一些

代码如下

复制代码

function safe_replace($string) {
$string = str_replace(' ','',$string);
$string = str_replace(''','',$string);
$string = str_replace(''','',$string);
$string = str_replace('*','',$string);
$string = str_replace('"','"',$string);
$string = str_replace("'",'',$string);
$string = str_replace('"','',$string);
$string = str_replace(';','',$string);
$string = str_replace('<','<',$string);
$string = str_replace('>','>',$string);
$string = str_replace("{",'',$string);
$string = str_replace('}','',$string);
return $string;
}

更全面的

代码如下

复制代码

//处理提交的数据
function htmldecode($str) {
if (empty ( $str ) || "" == $str) {
return "";
}

$str = strip_tags ( $str );
$str = htmlspecialchars ( $str );
$str = nl2br ( $str );
$str = str_replace ( "?", "", $str );
$str = str_replace ( "*", "", $str );
$str = str_replace ( "!", "", $str );
$str = str_replace ( "~", "", $str );
$str = str_replace ( "$", "", $str );
$str = str_replace ( "%", "", $str );
$str = str_replace ( "^", "", $str );
$str = str_replace ( "^", "", $str );
$str = str_replace ( "select", "", $str );
$str = str_replace ( "join", "", $str );
$str = str_replace ( "union", "", $str );
$str = str_replace ( "where", "", $str );
$str = str_replace ( "insert", "", $str );
$str = str_replace ( "delete", "", $str );
$str = str_replace ( "update", "", $str );
$str = str_replace ( "like", "", $str );
$str = str_replace ( "drop", "", $str );
$str = str_replace ( "create", "", $str );
$str = str_replace ( "modify", "", $str );
$str = str_replace ( "rename", "", $str );
$str = str_replace ( "alter", "", $str );
$str = str_replace ( "cast", "", $str );

$farr = array ("//s+/", //过滤多余的空白
"/<(//?)(img|script|i?frame|style|html|body|title|link|meta|/?|/%)([^>]*?)>/isU", //过滤