pass query string get value into url link - php

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>";
}
?>

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>";
}
?>

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.