Add www to url in string

Question

I am trying to add www to php url, but I my code is not working properly in some cases:

$url="http://example.com";
$url=str_replace(array("http://www.","https://www."),array("http://","https://"),$url);
$url=str_replace(array("http://","https://"),array("http://www.","https://www."),$url);
echo $url; //http://www.example.com

But in this case:

$url="https://www.example.com/href.php?redir=http://other-nonwww-server.com";
$url=str_replace(array("http://www.","https://www."),array("http://","https://"),$url);
$url=str_replace(array("http://","https://"),array("http://www.","https://www."),$url);
echo $url; //https://www.example.com/href.php?redir=http://www.other-nonwww-server.com

it changed the request.

Answer 1

Don't use string manipulation methods when PHP offers proper URL parsing methods:

Do this:

<?php
$url="https://example.com:8080/href.php?redir=http://other-nonwww-server.com";

$bits = parse_url($url);

$newHost = substr($bits["host"],0,4) !== "www."?"www.".$bits["host"]:$bits["host"];

$url2 = $bits["scheme"]."://".$newHost.(isset($bits["port"])?":".$bits["port"]:"").$bits["path"].(!empty($bits["query"])?"?".$bits["query"]:"");;

print_r($url2);

Prints:

https://www.example.com:8080/href.php?redir=http://other-nonwww-server.com

Example at https://eval.in/798862