I get a lot of questions in regards to how to use the WHMCS licensing addon which is why I wrote a post a while back which described how to get the code working. That guide is outdated and did not show any code which is why I want to write a new guide with a little bit of code, but not enough to disclose how the whmcs licensing addon works.

When you purchase the WHMCS licensing addon you will receive several files but you will only have to worry about one for this guide which is the check_sample_code.php file. This is an example by WHMCS to show you how the code should be implemented in your script, plugin or theme. I will now walk through the example file and show you which parts are important and what they do.

inside the function check_license() we have the following code.

$whmcsurl = "http://www.yourdomain.com/whmcs/";
    $licensing_secret_key = "abc123";

These almost explain themselves and WHMCS even has some commenting to explain how to modify them. The first variable $whmcsurl should be equal to your whmcs installation and the other variable $licensing_secret_key is your secret key that you use when creating the product that you will be licensing.

those are all the changes you should make to the check_license() function. You could basically copy the check license function (all of it) and paste it into your script, plugin, or theme. The header file is always a good place to either have the code or include the file which contains the code for the function check_license(). Check php’s include function for more information on how to do this.

Now, let’s go past the check_license() function and move down to $licensekey, this is very important and should always be equal to the license you generate in WHMCS. This is the key used to check if a license is valid or not. Next is the local key ($localkey), don’t worry about this, its a local key used for logging and you could change it up if you would like, but i wouldn’t touch it.

This line actually calls the function that will talk to your WHMCS and check if the license is valid or not.

$results = check_license($licensekey,$localkey);

You need to include this in your php file after the $licensekey and $localkey are defined. If you do not include this function then your script won’t check if the license is valid.

Now the results of the function check_license() is stored in the variable $results as an array. The status of the license will be stored in this key.

$results["status"]

We can now check if the license was valid using the included else if statement WHMCS uses.

if ($results["status"]=="Active") {
    # Allow Script to Run
    if ($results["localkey"]) {
        # Save Updated Local Key to DB or File
        $localkeydata = $results["localkey"];
    }
} elseif ($results["status"]=="Invalid") {
    # Show Invalid Message
} elseif ($results["status"]=="Expired") {
    # Show Expired Message
} elseif ($results["status"]=="Suspended") {
    # Show Suspended Message
}

This is very simple but can get confusing for some so I will make a quick example of my own script which I want to use the license check on.

So here is my script which I want to license.

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It simply takes two numbers and adds them. Now I want to show my script only if the license is valid, so I can add an if statement to make this check. I also need to include the check_license() function which I added in a file called licensefunction.php.

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Now the script will only show if there is a valid license otherwise the page will be blank, but I want to show an error if the license is invalid so that the user doesn’t get confused.

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This will echo the error if the license was not valid, I could of course add different errors for an invalid, suspended, or expired license but this will be ok for my script, the user will know something is wrong.

For larger scripts I could terminate the loading of a page by simply adding a die() function at the top.

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?>

Now the script will stop loading at the die() function if the license is not active, so none of the code below the die statement will be presented. If the license is active the die function will never be called and the script will continue to run normally.

To make your licensed script, plugin, or theme even more secure I would recommend using something like IonCube loader which WHMCS uses on their own encrypted files.