php - Regular expression pattern to match URL with or without http://www

Question

I'm not very good at regular expressions at all.

I've been using a lot of framework code to date, but I'm unable to find one that is able to match a URL like http://www.example.com/etcetc, but it is also is able to catch something like www.example.com/etcetc and example.com/etcetc.

Answer 1

For matching all kinds of URLs, the following code should work:

<?php
    $regex = "((https?|ftp)://)?"; // SCHEME
    $regex .= "([a-z0-9+!*(),;?&=$_.-]+(:[a-z0-9+!*(),;?&=$_.-]+)?@)?"; // User and Pass
    $regex .= "([a-z0-9-.]*).(([a-z]{2,4})|([0-9]{1,3}.([0-9]{1,3}).([0-9]{1,3})))"; // Host or IP
    $regex .= "(:[0-9]{2,5})?"; // Port
    $regex .= "(/([a-z0-9+$_%-].?)+)*/?"; // Path
    $regex .= "(?[a-z+&$_.-][a-z0-9;:@&%=+/$_.-]*)?"; // GET Query
    $regex .= "(#[a-z_.-][a-z0-9+$%_.-]*)?"; // Anchor
?>

Then, the correct way to check against the regex is as follows:

<?php
   if(preg_match("~^$regex$~i", 'www.example.com/etcetc', $m))
      var_dump($m);

   if(preg_match("~^$regex$~i", 'http://www.example.com/etcetc', $m))
      var_dump($m);
?>

Courtesy: Comments made by splattermania in the PHP manual: http://php.net/manual/en/function.preg-match.php

RegEx Demo in regex101