PHP function to make slug (URL string)

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).

Answer

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