Optimized PHP slugify function to create clean SEO friendly urls

Code snippet

/**
 * @param $title
 * @return mixed|string|string[]|null
 */
function slugify($title) {
  // Convert the title to lowercase
  $slug = strtolower($title);
  // Replace spaces with dashes
  $slug = str_replace(' ', '-', $slug);
  // Remove special characters except dashes and alphanumeric characters
  $slug = preg_replace('/[^a-z0-9-]/', '', $slug);
  // Remove double dashes
  $slug = preg_replace('/-+/', '-', $slug);
  // Trim dashes from the beginning and end
  $slug = trim($slug, '-');
  return $slug;
}

Step-by-Step Explanation:

1. Convert to Lowercase:

   Input: Original title or string.
   Action: Convert the entire string to lowercase using strtolower.
   Output: A lowercase version of the input string.

2. Replace Spaces with Dashes:

   Input: Lowercased string from step 1.
   Action: Replace spaces with dashes using str_replace.
   Output: A string with spaces replaced by dashes.

3. Remove Special Characters:

   Input: String with spaces replaced by dashes.
   Action: Use regular expression preg_replace to remove non-alphanumeric characters.
   Output: A string containing only alphanumeric characters and dashes.

4. Remove Double Dashes:

   Input: Alphanumeric string with dashes.
   Action: Apply preg_replace to eliminate consecutive dashes.
   Output: A string without consecutive dashes.

5. Trim Leading and Trailing Dashes:

   Input: String without consecutive dashes.
   Action: Use trim to remove leading or trailing dashes.
   Output: A final slug without leading or trailing dashes.

6. Return Result:

   Input: Finalized slug.
   Action: Return the resulting slug as the output of the function.
   Output: A clean, URL-friendly slug derived from the original title or string.

The importance of having clean and concise URL segments from a SEO perspective