PHP过滤指定字符串，过滤危险字符

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;
}