php过滤html字符串，防止SQL注入的实例代码

php过滤html字符串，防止SQL注入,用函数把将要写入到数据库的字符串处理下，过滤非法信息，以及恶意的html代码！

代码：

//php 批量过滤post,get敏感数据
if (get_magic_quotes_gpc()) {
$_GET = stripslashes_array($_GET);
$_POST = stripslashes_array($_POST);
}

function stripslashes_array(&$array) {
while(list($key,$var) = each($array)) {
if ($key != 'argc' && $key != 'argv' && (strtoupper($key) != $key || ''.intval($key) == "$key")) {
if (is_string($var)) {
$array[$key] = stripslashes($var);
}
if (is_array($var)) {
$array[$key] = stripslashes_array($var);
}
}
}
return $array;
}
//过滤
function htmlencode($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_replace(chr(32)," ",$str);
$str=str_replace(chr(9)," ",$str);
$str=str_replace(chr(9)," ",$str);
$str=str_replace(chr(34),"&",$str);
$str=str_replace(chr(39),"'",$str);
$str=str_replace(chr(13),"
",$str);
$str=str_replace("'","''",$str);
$str=str_replace("select","select",$str);
$str=str_replace("SCRIPT","SCRIPT",$str);
$str=str_replace("script","script",$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;
}

//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_replace(" ",chr(32),$str);
$str=str_replace(" ",chr(9),$str);
$str=str_replace(" ",chr(9),$str);
$str=str_replace("&",chr(34),$str);
$str=str_replace("'",chr(39),$str);
$str=str_replace("
",chr(13),$str);
$str=str_replace("''","'",$str);
return $str;
}

// 函数：string_filter($string, $match_type=1)
// 功能：过滤非法内容
// 参数：
// $string 需要检查的字符串
// $match_type 匹配类型,1为精确匹配, 2为模糊匹配，默认为1
//
// 返回：有非法内容返回True，无非法内容返回False
// 其他：非法关键字列表保存在txt文件里, 分为普通非法关键字和严重非法关键字两个列表
// 作者：heiyeluren
// 时间：2006-1-18
//
//======================================================================
function lib_lawless_string_filter($string, $match_type=1)
{
//字符串空直接返回为非法
$string = trim($string);
if (empty($string))
{
return false;
}
//获取重要关键字列表和普通关键字列表
$common_file = "common_list.txt"; //通用过滤关键字列表
$signify_file = "signify_list.txt"; //重要过滤关键字列表
//如果任何列表文件不存在直接返回false，否则把两个文件列表读取到两个数组里
if (!file_exists($common_file) || !file_exists($signify_file))
{
return false;
}
$common_list = file($common_file);
$signify_list = file($signify_file);

//精确匹配
if ($match_type == 1)
{
$is_lawless = exact_match($string, $common_list);
}

//模糊匹配
if ($match_type == 2)
{
$is_lawless = blur_match($string, $common_list, $signify_list);
}

//判断检索结果数组中是否有数据，如果有，证明是非法的
if (is_array($is_lawless) && !empty($is_lawless))
{
return true;
}
else
{
return false;
}
}

//---------------------
// 精确匹配,为过滤服务
//---------------------
function exact_match($string, $common_list)
{
$string = trim($string);
$string = lib_replace_end_tag($string);

//检索普通过滤关键字列表
foreach($common_list as $block)
{
$block = trim($block);
if (preg_match("/^$string$/i", $block))
{
$blist[] = $block;
}
}
//判断有没有过滤内容在数组里
if (!empty($blist))
{
return array_unique($blist);
}

return false;
}

//----------------------
// 模糊匹配,为过滤服务
//----------------------
function blur_match($string, $common_list, $signify_list)
{
$string = trim($string);
$s_len = strlen($string);
$string = lib_replace_end_tag($string);

//检索普通过滤关键字列表
foreach($common_list as $block)
{
$block = trim($block);
if (preg_match("/^$string$/i", $block))
{
$blist[] = $block;
}
}
//检索严重过滤关键字列表
foreach($signify_list as $block)
{
$block = trim($block);
if ($s_len>=strlen($block) && preg_match("/$block/i", $string))
{
$blist[] = $block;
}
}
//判断有没有过滤内容在数组里
if (!empty($blist))
{
return array_unique($blist);
}

return false;
}

//--------------------------
// 替换HTML尾标签,为过滤服务
//--------------------------
function lib_replace_end_tag($str)
{
if (empty($str)) return false;
$str = htmlspecialchars($str);
$str = str_replace( '/', "", $str);
$str = str_replace("\\", "", $str);
$str = str_replace(">", "", $str);
$str = str_replace("<", "", $str);
$str = str_replace("<script>", "", $str); <br />$str = str_replace("</script>", "", $str);
$str = str_replace("<script>", "", $str); <br />$str = str_replace("</script>", "", $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_replace(" ",chr(32),$str);
$str=str_replace(" ",chr(9),$str);
$str=str_replace(" ",chr(9),$str);
$str=str_replace("&",chr(34),$str);
$str=str_replace("'",chr(39),$str);
$str=str_replace("
",chr(13),$str);
$str=str_replace("''","'",$str);
$str=str_replace("css","'",$str);
$str=str_replace("CSS","'",$str);

return $str;

//HTML标签，可以作为扩展过滤
/*
$tags = array("/html", "/head", "/body", "/div", "/span", "/DOCTYPE", "/title", "/link", "/meta", "/style", "/p", "/h1,", "/h2,", "/h3,", "/h4,", "/h5,", "/h6", "/strong", "/em", "/abbr", "/acronym", "/address", "/bdo", "/blockquote", "/cite", "/q", "/code", "/ins", "/del", "/dfn", "/kbd", "/pre", "/samp", "/var", "/br", "/a", "/img", "/area", "/map", "/object", "/param", "/ul", "/ol", "/li", "/dl", "/dt", "/dd", "/table", "/tr", "/td", "/th", "/tbody", "/thead", "/tfoot", "/col", "/colgroup", "/caption", "/form", "/input", "/textarea", "/select", "/option", "/optgroup", "/button", "/label", "/fieldset", "/legend", "/script", "/noscript", "/b", "/i", "/tt", "/sub", "/sup", "/big", "/small", "/hr" );
*/

}

代码：

引用是直接这样：
$xxx = htmlspecialchars($_POST['xxx']);
或者
$xxx = htmlspecialchars($_GET['xxx']);