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PHP : Function Reference : URL Functions

URL Functions


Dealing with URL strings: encoding, decoding and parsing.


No external libraries are needed to build this extension.


There is no installation needed to use these functions; they are part of the PHP core.

Runtime Configuration

This extension has no configuration directives defined in php.ini.

Resource Types

This extension has no resource types defined.

Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

The following constants are meant to be used with parse_url() and are available since PHP 5.1.2.

PHP_URL_SCHEME (integer)
PHP_URL_HOST (integer)
PHP_URL_PORT (integer)
PHP_URL_USER (integer)
PHP_URL_PASS (integer)
PHP_URL_PATH (integer)
PHP_URL_QUERY (integer)

Table of Contents

base64_decode — Decodes data encoded with MIME base64
base64_encode — Encodes data with MIME base64
get_headers — Fetches all the headers sent by the server in response to a HTTP request
get_meta_tags — Extracts all meta tag content attributes from a file and returns an array
http_build_query — Generate URL-encoded query string
parse_url — Parse a URL and return its components
rawurldecode — Decode URL-encoded strings
rawurlencode — URL-encode according to RFC 1738
urldecode — Decodes URL-encoded string
urlencode — URL-encodes string

Code Examples / Notes » ref.url


You should have named your form field "organization[]" (notice the square brackets), instead of just organization. When using square brackets, the get/post request is interpreted by PHP as an array.
If you follow this example you'll understand why it works the way it does:
$organization = 92;
$organization = 93;
// The second asignment overwrites the value of the first
// asignment. $organization === 93.
$organization[] = 92;
$organization[] = 93;
// The above is interpreted as appending data to an array
// named "$organization". $organization is an array
// consisting of the values 92 AND 93.
When submitting form fields with appended square brackets to their name, PHP interprets the submission using the same logic exposed above. Thus PHP automatically creates an array with all selected options if "$organization[]" is used as the field name.
  Daniel Berstein.


When using a multiple select on a form, I ran into a little issue of only receiving the last value form the select box.
I had a select box named organization_id with two values (92 and 93).
To get the values of both, I had to use the following:
$temp_array = split("&", $_SERVER['QUERY_STRING']);
foreach($temp_array as $key=>$value){
if(substr($value, 0, 15) == "organization_id"){
$_GET['organizations'][] = substr($value, 15, strlen($value));
this results in a $_GET array like this :
   [page] => idea_submission
   [organization_id] => 93
   [organizations] => Array
           [0] => =92
           [1] => =93


Warning: when the PHP engine runs for your hosted web site, it may execute on a domain name which is completely different than the one the user requested in its browser. Many free web hosting site use proxies and/or multiple DNS entries for your hosted web site. This means that:
- the IP of the web server can change if multiple DNS entries are present (there may be several web servers running concurrently)
- reverse DNS name from the IP may give different domain name over time, or if the domain name is a CNAME only for a virtual web server hosting many domains
- the server running PHP may be different than the web server
- the web server may be hidden behind a proxy which balances the load between a farm of servers
- the queried host name in the HTTP headers may be different than the queried host name in the browser, if behind a redirecting proxy
- the actual path name of the ressource may be also different, with additional path elements: this is very common on free hosting servers, where you get a virtual CNAME domain, which gets translated by a proxy into an actual web server, and a domain-specific document root directory
So when thinking about using absolute path names you can retreive from PHP, beware that this may not be accurate to insert as absolute URL's in the HTML code built with PHP.
The best solution is then to ALWAYS USE relative URLs to reference documents and form scripts on your local server !
This applies to $PHP_SELF too, because it's an absolute pathname: don't use it directly but you can safely use basename($PHP_SELF) to reference your script within HTML forms:
<FORM method="GET" action="$self">


To check if a URL is valid, try to fopen() it. If fopen() results an error (returns false), then PHP cannot open the URL you asked. This is usually because it is not valid...


Note that $_SERVER["HTTP_REFERER"] may not include GET data that was included in the referring address, depending on the browser.  So if you rely on GET variables to generate a page, it's not a good idea to use HTTP_REFERER to smoothly "bounce" someone back to the page he/she came from.

ignacio paz posse

Note on the above: the point is that is that using $_SERVER['QUERY_STRING'] along with $PHP_SELF we will have passed whatever variables are already appended (as they might be needed for database queries)
example, given the following url: http://www.your_domain/somepage.php?variable=1;
using $PHP_SELF" we are passing
[scheme]:(http://), [host]: www.your_domain/  and [path]: somepage.php
adding $_SERVER['QUERY_STRING'], we pass that, plus [query]: variable=1


Note also that the URL shown in $HTTP_REFERER is not always the URL of the web page where the user clicked to invoke the PHP script.
This may instead be a document of your own web site, which contains an HTML element whose one attribute references the script. Note also that the current page fragment (#anchor) may be transmitted or not with the URL, depending on the browser.
<FRAME src="your-page-script.php"8>
<IMAGE src="your-image-script.php">
In such case, browsers should transmit the URL of the container document, but some still persist in using the previous document in the browser history, and this could cause a different $HTTP_REFERER value be sent when the user comes back to the document referencing your script. If you wanna be sure that the actual current document or previous document in the history is sent, use client-side JavaScript to send it to your script:
<SCRIPT language="JavaScript"><!--
document.writeln('<FRAME src="your-page-script.php?js=1&amp;ref=' +
document.location + '">');
<FRAME src="your-page-script.php?js=0">
And then check the value of $js in your page script to generate appropriate content when the remote user agent does not support client-side scripts (such as most index/scan robots, some old or special simplified browsers, or browsers with JavaScript disabled by their users).

job oberio

just want to share some tip:
my visitors usually type
in their browser (note: no www)
and i want them to automatically change the url
to use www.
(from to
The solution is:
you can add the ff code to your existing index.php script
if  ($HTTP_HOST=="")
header("Location:"); die();
~~~ your existing codes here ~~~
hope that helps


just a side note to the above you will need to add the ?


If you want to get the filename requested on a global error page like a 404, just use this code...
// get the full var...
// part[1] is the url...
// part[0] is the http code (404, etc).
if(strpos($page,";")>0) {
  $pageParts = explode(";",$page);
  $page = $pageParts[1];
// get only the filename...
$page = basename($page);


If you got a server which got only one subdomain and you can't add a subdomain you can easily create your own "subdomain script". You may create a file "index.php" or what ever your defaul filename is in the webpage root directory and add the following PHP Code:
// Get possible subdomain
$full_url = sprintf($HTTP_HOST);
$subdomain = "";
for($i = 0;$i<=strlen($full_url);$i++)
 $dummy = substr($full_url,$i,1);
 if($dummy == ".")
 $subdomain = $subdomain.$dummy;
// Get Subdomain List
if ($subdomain <> "www")
   case "download":
     $real_url = "";
   case "contact":
     $real_url = "";
 header( "location: $real_url\r\n" );


if you do this, it will be easier :
echo "http://{$HTTP_HOST}{$REQUEST_URI}";

pawel dot lesniak

How do I go and encode an URL, but EVERYTHING is encoded. As such:
This one does what you want
$text = '';
$output = '';
$tab_text = str_split($text);
foreach ($tab_text as $id=>$char){
 $hex = dechex(ord($char));
 $output .= '%' . $hex;
echo $output;


How do I go and encode an URL, but EVERYTHING is encoded. As such:
(note: I hand-url-encoded it)
Here is the URL-Encoded url, clickable (the http:// part shows up twice)


Following method do not show the URL in user browser (as the author claimed) if the code resides in the source page of  FRAME or IFRAME (say SRC="sourcepage.php") . In that case the URL of the SOURCE page is displayed.
$url = sprintf("%s%s%s","http://",$HTTP_HOST,$REQUEST_URI);
echo "$url";
Expected result: http://localhost/urltest/framedpage.php
Actual result: http://localhost/urltest/sourcepage.php


Each %xx represents a letter. You would need to remove %68%74%74%70%3a%2f%2f (http://) from the beginning.


May be this is obvious but helps me since I found it:
If I want to append a variable to the url and pass it to the same page. ( in this example I'm using action=email to include an email form on the user click) i do:
// ...
<a href="<? echo $PHP_SELF,'?',$_SERVER['QUERY_STRING'],'&action=email' ?>">email to us</a>
// ...
/* somewhere in the the page (in my case at the bottom) I have: */
<? if ($action=='email') include('emailForm.htm'); ?>

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