PHP function to make slug (URL string)

Question

Instead of a lengthy replace, try this one:

public static function slugify($text, string $divider = '-')
{
  // replace non letter or digits by divider
  $text = preg_replace('~[^\pL\d]+~u', $divider, $text);

  // transliterate
  $text = iconv('utf-8', 'us-ascii//TRANSLIT', $text);

  // remove unwanted characters
  $text = preg_replace('~[^-\w]+~', '', $text);

  // trim
  $text = trim($text, $divider);

  // remove duplicate divider
  $text = preg_replace('~-+~', $divider, $text);

  // lowercase
  $text = strtolower($text);

  if (empty($text)) {
    return 'n-a';
  }

  return $text;
}

This was based off the one in Symfony's Jobeet tutorial.

Update

Since this answer is getting some attention, I'm adding some explanation.

The solution provided will essentially replace everything except A-Z, a-z, 0-9, & - (hyphen) with - (hyphen). So, it won't work properly with other unicode characters (which are valid characters for a URL slug/string). A common scenario is when the input string contains non-English characters.

Only use this solution if you're confident that the input string won't have unicode characters which you might want to be a part of output/slug.

Eg. "नारी शक्ति" will become "----------" (all hyphens) instead of "नारी-शक्ति" (valid URL slug).

Original Answer

How about...

$slug = strtolower(trim(preg_replace('/[^A-Za-z0-9-]+/', '-', $string)));

?

If you have intl extension installed, you can use Transliterator::transliterate function to create a slug easily.

<?php
$string = 'Namnet på bildtävlingen';
$slug = \Transliterator::createFromRules(
    ':: Any-Latin;'
    . ':: NFD;'
    . ':: [:Nonspacing Mark:] Remove;'
    . ':: NFC;'
    . ':: [:Punctuation:] Remove;'
    . ':: Lower();'
    . '[:Separator:] > \'-\''
)
    ->transliterate( $string );
echo $slug; // namnet-pa-bildtavlingen
?>

Note: I have taken this from wordpress and it works!!

Use it like this:

echo sanitize('testing this link');

Code

//taken from wordpress
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;
}

//taken from wordpress
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 sanitize_title_with_dashes taken from wordpress
function sanitize($title) {
    $title = strip_tags($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);
    $title = preg_replace('/[^%a-z0-9 _-]/', '', $title);
    $title = preg_replace('/\s+/', '-', $title);
    $title = preg_replace('|-+|', '-', $title);
    $title = trim($title, '-');

    return $title;
}

It is always a good idea to use existing solutions that are being supported by a lot of high-level developers. The most popular one is https://github.com/cocur/slugify. First of all, it supports more than one language, and it is being updated.

If you do not want to use the whole package, you can copy the part that you need.

Here is an other one, for example " Title with strange characters ééé A X Z" becomes "title-with-strange-characters-eee-a-x-z".

/**
 * Function used to create a slug associated to an "ugly" string.
 *
 * @param string $string the string to transform.
 *
 * @return string the resulting slug.
 */
public static function createSlug($string) {

    $table = array(
            'Š'=>'S', 'š'=>'s', 'Đ'=>'Dj', 'đ'=>'dj', 'Ž'=>'Z', 'ž'=>'z', 'Č'=>'C', 'č'=>'c', 'Ć'=>'C', 'ć'=>'c',
            'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A', 'Ä'=>'A', 'Å'=>'A', 'Æ'=>'A', 'Ç'=>'C', 'È'=>'E', 'É'=>'E',
            'Ê'=>'E', 'Ë'=>'E', 'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I', 'Ñ'=>'N', 'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O',
            'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O', 'Ù'=>'U', 'Ú'=>'U', 'Û'=>'U', 'Ü'=>'U', 'Ý'=>'Y', 'Þ'=>'B', 'ß'=>'Ss',
            'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a', 'æ'=>'a', 'ç'=>'c', 'è'=>'e', 'é'=>'e',
            'ê'=>'e', 'ë'=>'e', 'ì'=>'i', 'í'=>'i', 'î'=>'i', 'ï'=>'i', 'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o',
            'ô'=>'o', 'õ'=>'o', 'ö'=>'o', 'ø'=>'o', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'ý'=>'y', 'ý'=>'y', 'þ'=>'b',
            'ÿ'=>'y', 'Ŕ'=>'R', 'ŕ'=>'r', '/' => '-', ' ' => '-'
    );

    // -- Remove duplicated spaces
    $stripped = preg_replace(array('/\s{2,}/', '/[\t\n]/'), ' ', $string);

    // -- Returns the slug
    return strtolower(strtr($string, $table));


}