php下过滤html代码的函数 提高程序安全性

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; 
}

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; 
}