转义特殊字符 php

public static function filterString2($string)
{
    $patterns = array();
    $patterns[0] = "/!/"; $patterns[1] = "/@/"; $patterns[2] = "/#/";
    $patterns[3] = "/$/"; $patterns[4] = "/%/"; $patterns[5] = "/&/";
    $patterns[6] = "/*/"; $patterns[7] = "/(/"; $patterns[8] = "/)/";
    $patterns[9] = "/-/"; $patterns[10] = "/=/"; $patterns[11] = "/_/";
    $patterns[12] = "/+/";

    $replacements = array();
    $replacements[0] = "!"; $replacements[1] = "@"; $replacements[2] = "#";
    $replacements[3] = "$"; $replacements[4] = "\%"; $replacements[5] = "&";
    $replacements[6] = "\*"; $replacements[7] = "\("; $replacements[8] = "\)";
    $replacements[9] = "-"; $replacements[10] = "="; $replacements[11] = "\_";
    $replacements[12] = "\+";

    return preg_replace($patterns, $replacements, $string);
}