urlparts.php

<?php declare(strict_types=1);

/**
 * Copyright (c) 2007-2021, Jos de Ruijter <jos@dutnie.nl>
 */

/**
 * Trait with code handling URL validation and disassembly. Returns null if a
 * URL fails the syntax check. Returns an array with the URLs parts on success.
 * Missing parts are represented by an empty string, a missing port part by
 * (int) 0.
 *
 * For reference: RFC 3986, RFC 1034 section 3.5, RFC 1123 section 2.1
 *
 * Additional notes:
 *  - The scheme should either be http or https. For URLs without a scheme, http
 *    is assumed.
 *  - User part in authority is not recognized and will not validate.
 *  - IPv6 addresses will not validate.
 *  - Square brackets must be percent encoded.
 */
trait urlparts
{
	private string $regexp_callback = '';
	private string $regexp_complete = '';

	private function get_urlparts(string $url): ?array
	{
		/**
		 * Assemble the regular expression if not already done so.
		 */
		if ($this->regexp_complete === '') {
			$domain = '(?<domain>[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?(?:\.[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?)*)';
			$tld = '(?<tld>[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?)';
			$fqdn = '(?<fqdn>'.$domain.'\.'.$tld.')\.?';
			$ipv4address = '(?<ipv4address>(?:25[0-5]|(?:2[0-4]|1[0-9]|[1-9])?[0-9])(?:\.(?:25[0-5]|(?:2[0-4]|1[0-9]|[1-9])?[0-9])){3})';
			$port = '(?<port>(?:6553[0-5]|(?:655[0-2]|(?:65[0-4]|(?:6[0-4]|[1-5][0-9]|[1-9])[0-9]|[1-9])[0-9]|[1-9])?[0-9]))';
			$authority = '(?<authority>(?:'.$ipv4address.'|'.$fqdn.')(?::'.$port.')?)';
			$unreserved = '[a-z0-9_.~-]';
			$pct_encoded = '%[0-9a-f]{2}';
			$sub_delims = '[!$&\'()*+,;=]';
			$pchar = '(?:'.$unreserved.'|'.$pct_encoded.'|'.$sub_delims.'|[:@])';
			$fragment = '(?<fragment>(?:#(?:'.$pchar.'|[\/?])*)?)';
			$path = '(?<path>(?:\/\/?(?:'.$pchar.'+\/?)*)?)';
			$query = '(?<query>(?:\?(?:'.$pchar.'|[\/?])*)?)';
			$scheme = '(?:(?<scheme>https?):\/\/)';
			$this->regexp_callback = '/^'.$scheme.'?'.$authority.'/i';
			$this->regexp_complete = '/^(?<url>'.$scheme.'?'.$authority.$path.$query.$fragment.')$/i';
		}

		/**
		 * Convert scheme and authority to lower case.
		 */
		$url = preg_replace_callback($this->regexp_callback, function (array $matches): string {
			return strtolower($matches[0]);
		}, $url);

		/**
		 * Validate the URL.
		 */
		if (!preg_match($this->regexp_complete, $url, $matches, PREG_UNMATCHED_AS_NULL)) {
			return null;
		}

		/**
		 * The TLD may not consist of all digits.
		 */
		if (!is_null($matches['tld']) && preg_match('/^\d+$/', $matches['tld'])) {
			return null;
		}

		/**
		 * The FQDN (excluding trailing dot) may not exceed 253 characters.
		 */
		if (!is_null($matches['fqdn']) && strlen($matches['fqdn']) > 253) {
			return null;
		}

		/**
		 * If the URL has no scheme, http is assumed.
		 */
		if (is_null($matches['scheme'])) {
			$matches['scheme'] = 'http';
			$matches['url'] = 'http://'.$matches['url'];
		}

		/**
		 * Create an array with all parts of the URL. Cast the port number to integer.
		 * 0 means no port. For the other parts return an empty string instead of null.
		 */
		$urlparts['port'] = (is_null($matches['port']) ? 0 : (int) $matches['port']);

		foreach (['url', 'scheme', 'authority', 'ipv4address', 'fqdn', 'domain', 'tld', 'path', 'query', 'fragment'] as $part) {
			$urlparts[$part] = $matches[$part] ?? '';
		}

		return $urlparts;
	}
}