If you’re a loyal reader of my blog you’ll know that I am a huge fan of WordPress. One of the great features that really floats my boat is the sanitize functionality used to convert a post title into a SEO-friendly URL permalink. In fact, they have many sanitize functions dedicated to converting all sorts of text (author names, file names, and keys to name a few).

Today I wanted to implement a similar feature for a project I was working on, converting a standard string of text like “How to Borrow WordPress’s URL Sanitize Function” into “how-to-borrow-wordpresss-url-sanitize-function.” After a big of digging (namely a grep for “sanitize”), I narrowed it down to the right function and helper functions in the WordPress core. The code that appears below is lifted directly from wp-includes/formatting.php without any modifications. This should be update to date as of WordPress 3.4.1.

So you won’t have to do the work I did–and you know I hate to redo work if I can help it–I’ve supplied exactly the functions you need to replicate WordPress’s string sanitize function in PHP. Here it is:

function sanitize_title_with_dashes($title, $raw_title = '', $context = 'display') {
	$title = strip_tags($title);
	// Preserve escaped octets.
	$title = preg_replace('|%([a-fA-F0-9][a-fA-F0-9])|', '---$1---', $title);
	// Remove percent signs that are not part of an octet.
	$title = str_replace('%', '', $title);
	// Restore octets.
	$title = preg_replace('|---([a-fA-F0-9][a-fA-F0-9])---|', '%$1', $title);

	if (seems_utf8($title)) {
		if (function_exists('mb_strtolower')) {
			$title = mb_strtolower($title, 'UTF-8');
		}
		$title = utf8_uri_encode($title, 200);
	}

	$title = strtolower($title);
	$title = preg_replace('/&.+?;/', '', $title); // kill entities
	$title = str_replace('.', '-', $title);

	if ( 'save' == $context ) {
		// Convert nbsp, ndash and mdash to hyphens
		$title = str_replace( array( '%c2%a0', '%e2%80%93', '%e2%80%94' ), '-', $title );

		// Strip these characters entirely
		$title = str_replace( array(
			// iexcl and iquest
			'%c2%a1', '%c2%bf',
			// angle quotes
			'%c2%ab', '%c2%bb', '%e2%80%b9', '%e2%80%ba',
			// curly quotes
			'%e2%80%98', '%e2%80%99', '%e2%80%9c', '%e2%80%9d',
			'%e2%80%9a', '%e2%80%9b', '%e2%80%9e', '%e2%80%9f',
			// copy, reg, deg, hellip and trade
			'%c2%a9', '%c2%ae', '%c2%b0', '%e2%80%a6', '%e2%84%a2',
		), '', $title );

		// Convert times to x
		$title = str_replace( '%c3%97', 'x', $title );
	}

	$title = preg_replace('/[^%a-z0-9 _-]/', '', $title);
	$title = preg_replace('/\s+/', '-', $title);
	$title = preg_replace('|-+|', '-', $title);
	$title = trim($title, '-');

	return $title;
}
function seems_utf8($str) {
	$length = strlen($str);
	for ($i=0; $i < $length; $i++) {
		$c = ord($str[$i]);
		if ($c < 0x80) $n = 0; # 0bbbbbbb
		elseif (($c & 0xE0) == 0xC0) $n=1; # 110bbbbb
		elseif (($c & 0xF0) == 0xE0) $n=2; # 1110bbbb
		elseif (($c & 0xF8) == 0xF0) $n=3; # 11110bbb
		elseif (($c & 0xFC) == 0xF8) $n=4; # 111110bb
		elseif (($c & 0xFE) == 0xFC) $n=5; # 1111110b
		else return false; # Does not match any model
		for ($j=0; $j<$n; $j++) { # n bytes matching 10bbbbbb follow ?
			if ((++$i == $length) || ((ord($str[$i]) & 0xC0) != 0x80))
				return false;
		}
	}
	return true;
}
function utf8_uri_encode( $utf8_string, $length = 0 ) {
	$unicode = '';
	$values = array();
	$num_octets = 1;
	$unicode_length = 0;

	$string_length = strlen( $utf8_string );
	for ($i = 0; $i < $string_length; $i++ ) {

		$value = ord( $utf8_string[ $i ] );

		if ( $value < 128 ) {
			if ( $length && ( $unicode_length >= $length ) )
				break;
			$unicode .= chr($value);
			$unicode_length++;
		} else {
			if ( count( $values ) == 0 ) $num_octets = ( $value < 224 ) ? 2 : 3;

			$values[] = $value;

			if ( $length && ( $unicode_length + ($num_octets * 3) ) > $length )
				break;
			if ( count( $values ) == $num_octets ) {
				if ($num_octets == 3) {
					$unicode .= '%' . dechex($values[0]) . '%' . dechex($values[1]) . '%' . dechex($values[2]);
					$unicode_length += 9;
				} else {
					$unicode .= '%' . dechex($values[0]) . '%' . dechex($values[1]);
					$unicode_length += 6;
				}

				$values = array();
				$num_octets = 1;
			}
		}
	}

	return $unicode;
}

Just copy and paste all this code somewhere and call the sanitize_title_with_dashes("Supply Your Title to Be Sanitized Here") function, disregarding the remaining two parameters. Hope this helped you as much as it helped me. I will definitely be bookmarking this myself for my own personal use!