pass query string get value into url link

Question

I am trying to pass in a $_GET variable from a query string and pass it into a link to another page that has an application on it.

A customer will be directed to my page and the url will have the variable name merchantid. I need to take that on the home page, and pass it to the application page.

I've got it displaying on the home page as a test, so I know how to get it. I just need to know how to pass it the application page.

<?php
 if (empty($_GET)) {
 // no data passed by get
 echo "<a href='{site_url}application'>Application</a>";
 }
 else
 {
 // The value of the variable name is found
 echo "<a href='{site_url}application?merchantid=" .merchantid ."'><Application></a>";
 }
?>

My else link actually blows up currently.

Ok, here is my second try, with the same result. The link blows up when I pass in the merchantid into the url. Ex. www.mysite.com/?=merchantid=12345

<?php
 if (empty($_GET)) {
 // no data passed by get
 echo "<a href='{site_url}application'>Application</a>";
 }
 else
 {
 if(isset($_GET['merchantid'])){$merchantid = $_GET['merchantid'];}
 else{$merchantid = "DefaultMerchant";}
 echo "<a href='{$site_url}application?merchantid=" .$merchantid ."'><Application </a>"; 
 }
?>

• fast: where does merchantid (is $ missing?!) come from?
• fast: The problem is not clear - do you call the PHP with merchantid as a query parameter and ask how to access it? Does the PHP produce error messages??

Answer 1

Why your code is not working

You're not telling php that "merchantid" is a variable nor you're defining it.

Solution

Replace

echo "<a href='{site_url}application?merchantid=" .merchantid ."'><Application></a>";

With

if(isset($_GET['merchantid'])){$merchantid = $_GET['merchantid'];}
else{$merchantid = "";}
echo "<a href='{$site_url}application?merchantid=" .$merchantid ."'><Application></a>";
}

---

Updated code

<?php
$site_url = 'http://'.$_SERVER['HTTP_HOST'].'/';
 if (empty($_GET)) {
 // no data passed by get
 echo "<a href='{$site_url}application'>Application</a>";
 }
 else
 {
 if(isset($_GET['merchantid'])){$merchantid = $_GET['merchantid'];}
 else{$merchantid = "DefaultMerchant";}
 echo "<a href='{$site_url}application?merchantid=".$merchantid."'>Application</a>";
 }
?>

• andrew: where is $merchantid defined?
• MSTannu: unless you've previously assigned $_GET['merchatid'] to the variable $merchantid, you should use $_GET['merchantid'] instead. Also, dont forget the isset() check to avoid php notices.
• andrew: There is still a problem with this code; if $_GET['merchantid'] is not defined then $merchantid will not get defined and so will produce warnings when you try to read from it. +1 for edit
• user3456807: @andrew in the previous version of the answer the link wasn't echoed if $_GET['merchantid'] wasn't set, anyway I updated again my answer, this will output in any case the link :) Thanks for your feedback
• C.Coggins: See my revised code. I'm confused about how to display the link in my inner If statement. It looks like I'm not setting anything for the If statement.

Answer 2

$_GET is an array indexed by whatever values are in the query string. For example:

http://sit.url.com?merchantId=12&foo=bar

would place the following in the $_GET array:

$_GET['merchantId'] = "12"
$_GET['foo'] = "bar"

You will want a block in your code to initialize a $merchantId variable based on the presence of those values from $_GET:

//folks commonly use ternaries for this:
$merchantId = (isset($_GET['merchantId'])) ? $_GET['merchantId'] : false

Which is a shorthand way of stating:

if (isset($_GET['merhantId']) {
 $merchantId = $_GET['merchantId']
} else {
 $merchantId = false;
}

As Angelo and C.Coggins mentioned, don't forget the "$" in front of your variable in php.

Answer 3

You either need to assign $_GET['merchantid'] to $merchantid first, or replace $merchantid with $_GET['merchantid'] unless you have register_globals turned on, which you really shouldn't use.

So either add this:

$merchantid = $_GET['merchantid'];

or use this:

echo "<a href='{$site_url}application?merchantid=" . $_GET['merchantid'] . "'><Application></a>";

Besides that, as others pointed out, your original code is missing a $ before the variable name.

• andrew: you should check isset($_GET['merchantid']) otherwise either of your solutions could produce warnings
• Schlaus: True. I was only meaning to point out how to get the $_GET['merchantid'] value as the OP requested.