Regular Expression for validating URIs (PHP)

/**
 * Regular expression for matching URIs
 *
 * Significantly more accurate than any other method I've come across,
 * including the built in PHP methods.
 *
 * @author ChristianF
 * @link www.fagsoft.no
 * @licence http://creativecommons.org/licenses/by-sa/3.0/
 */
$RegExp = '#^(?:(?:(?:f|ht)tps?|dchub|sftp|steam)://)?'.
    // Username-password combos.
    '(?:\\w+(?::\\w+)?@)?'.

    // Domain or IP address
    '(?:((?:[\\w\\pL][\\w\\pL-]*(?<!\\-)\\.)+[a-z\\pL]{2,5})(?::\\d{1,5})?'.
    '|(?:(?:[0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}(?:[0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]))'.

    // URL Path
    '((?:(?<!/)/(?:\w(?:%[a-f\\d]{2}|[\\w\\., -])*)*)+(?:(?:\\.\\w{1,6})?'.
    // URL param
    '(\\?(?:(?:%[a-f\\d]{2}|[\\w\\.-])+=(?:%[a-f\\d]{2}|[\\w\\.-])+)(?:&(?:%[a-f\\d]{2}|[\\w\\.-])+(?:=(?:%[a-f\\d]{2}|[\\w\\.-])+)?)*&?)?'.
    ')?)?\\z#ui';