Question

Want to remove p2variable from url string, below are 3 cases if case 3 also remove ? sign.

case 1: http://www.domain.com/myscript.php?p1=xyz&p2=10&p3=ghj
result: http://www.domain.com/myscript.php?p1=xyz&p3=ghj

case 2: http://www.domain.com/myscript.php?p2=10&p3=ghj
result: http://www.domain.com/myscript.php?p3=ghj

case 3: http://www.domain.com/myscript.php?p2=10
result: http://www.domain.com/myscript.php

Want to achieve result with single preg_replace expression.

Answer 1

Don’t use regular expressions when dealing with URL values. It’s much easier (and safer) to handle them as a URL instead of plain text.

This could be one way to do it:

1. Split the url first and parse the query string
2. Take the parameter out
3. Rebuild the url

The below code is an example of such an algorithm:

// remove $qs_key from query string of $url
// return modified url value
function clean_url_qs($url, $qs_key)
{
    // first split the url in two parts (at most)
    $parts = explode('?', $url, 2);

    // check whether query string is passed        
    if (isset($parts[1])) {
      // parse the query string into $params
      parse_str($parts[1], $params);

      // unset if $params contains $qs_key
      if (array_key_exists($qs_key, $params)) {
          // remove key
          unset($params[$qs_key]);
          // rebuild the url
          return $parts[0] . 
              (count($params) ? '?' . http_build_query($params) : '');
      }
    }
    // no change required
    return $url;
}

Test code:

echo clean_url('http://www.domain.com/myscript.php?p1=xyz&p2=10&p3=ghj', 'p2'), "\n";
echo clean_url('http://www.domain.com/myscript.php?p2=10&p3=ghj', 'p2'), "\n";
echo clean_url('http://www.domain.com/myscript.php?p2=10', 'p2'), "\n";