function str2db($input, $strip_tags=true) {
	if(is_array($input)) {
		foreach($input as $key => $value) {
			$input[$key] = str2db($value);
		}
	} else {
		if(get_magic_quotes_gpc()) {
			if(ini_get('magic_quotes_sybase')){
					$input = str_replace("''", "'", $input);
			}
			else {
				$input = stripslashes($input);
			}
        }
		if($strip_tags) {
			$input = strip_tags($input);
		}
		$input = mysql_real_escape_string($input);
		$input = trim($input);
	}
	return $input;
}

function str2db($input, $strip_tags=true) {
	if(is_array($input)) {
		foreach($input as $key => $value) {
			$input[$key] = str2db($value);
		}
	} else {
		if(get_magic_quotes_gpc()) {
			if(ini_get('magic_quotes_sybase')){
					$input = str_replace("''", "'", $input);
			}
			else {
				$input = stripslashes($input);
			}
        }
		if($strip_tags) {
			$input = strip_tags($input);
		}
		$input = mysql_real_escape_string($input);
	}
	return trim($input);
}

This function can be used to sanitize single string variable or massive like POST, GET, COOKIE. It performs magic quotes gpc check, strip tags, trim and escape the dangerous signs with mysql_real_escape_string.

String to database (sanitize string for inserting in database)

post

PHP