php下过滤html代码的函数 提高程序安全性

以下为过滤html代码的函数：

function ihtmlspecialchars($string) {
if(is_array($string)) {
foreach($string as $key => $val) {
$string[$key] = ihtmlspecialchars($val);
}
} else {
$string = preg_replace('/&((#(\d{3,5}|x[a-fa-f0-9]{4})|[a-za-z][a-z0-9]{2,5});)/', '&\\1',
str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $string));
}
return $string;
}

php下过滤html代码的函数

function htmlencode($string) {
$string=trim($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);
$string=nl2br($string);
return $string;
}