Use PayPal for pay-per-post on WordPress.

Note: This article has been marked for a quality review and will soon be updated.

As you may know I like WordPress – it’s a great platform for building websites on. As you may not know is, I like PayPal – it’s an easy to way to safely make quick payments online. Now you may be asking what the hell I’m on about, have I been paid by WP and PayPal to go on about their services? Nope. Today I want to share with you an easy way to integrate these two fantastic services, to allow users of your site to pay each time they want to post on your site. For this we will be using the PayPal API, and a rather special page indeed which will allow your users to post from outside of the admin panel. If you didn’t know, there is already a tutorial on doing so entitled – Publishing to WordPress from outside the admin panel, so go ahead and check that out, and then come back over here.

So first let’s think about the theory behind this. We want users to go to our post-page, and then be asked to buy a token to post 1 article; we then want to send the user to PayPal, for them to pay us, and then be sent back to our site, where the same post-page now shows them everything they need to post an article. Sound good? Almost there, we need to make sure we prepare for something – say for instance the user has user paid, and there is a power-cut at their house, in that case they will have just lost the money they paid us, and will be rather angry that there is no way to get it back; so essentially we are covering for the user closing their browser without posting, having paid us. And for that we are going to enlist the help of the cookie monster! Nah, just kidding, we’ll stick to just one cookie for now – which will be placed on the user’s machine to tell our site that they have paid, and when they have posted we can alter the cookie to reflect that. So let’s go ahead and start with our posting page, place this code above your form.

<?php
if($_POST['payment_status']=="Completed"){
  $paid = true;
}else if($_COOKIE['activeToken']=="true") {
  $paid = true;
}else {
  $paid = false;
}

if(!$paid){ ?>

// User hasn't paid

<?php }else {  ?>

So what do we have here? Well at the top we can see we are checking to see if a posted variable is equal to “Completed” – this is something that PayPal gives us when the user has completed their transaction. We then set the $paid variable equal to true. Next we check a cookie to see if it’s value is “true”, and once again if this is true, we set $paid equal to true. And finally if neither of the above conditions validates we simply set the variable equal to false. Next we have an if statement which runs if $paid is equal to false – using the handy ! just before the variable. Now, after the else { statement is where you will want to put your form for posting an article, but not before you enter our crazy AJAX/Cookie-goodness code which follows.

<script type="text/javascript">
  $(document).ready(function(){
    var dataString = "cval=true";
    $.ajax({
      type: "POST",
      url: "<?php bloginfo('template_url') ?>/scripts/cookie.php",
      data: dataString,
    });
  });
</script>

// Your HTML goes here

<?php } ?>

Woah what the frick is that?! I hear you shouting. Right well let’s go from the top. First off we can see that we are using JavaScript, and also jQuery – so make sure it’s included, and we are also waiting for the DOM to have fully loaded everything before beginning our code. Then inside of this code we are setting up a variable named dataString and setting it’s value to “cval=true” – more on this soon. Then we create an AJAX call using jQuery which will POST to a URL which is in our theme folder in the scripts sub-folder, to a file named “cookie.php” the data in the variable dataString. Make sense? Hopefully it does. Now you might be thinking, but wait a moment, I don’t have a file called cookie.php, and even more annoying is that I don’t even have a folder called scripts in my theme directory. Well don’t worry – go ahead and create a new file called cookie.php in your theme directory, and if you tend to store scripts in another directory like me, go ahead and move it into that directory – just be sure to update the URL there – and if you didn’t know that handy bit of code that reads <?php bloginfo('template_url') ?> just spits out the URL of your theme’s directory. Now, copy and paste the following code into your new file.

<?php
$expire = 60 * 60 * 24 * 60 + time();
setcookie('activeToken', $_POST['cval'], $expire,'/');
?>

So what does that code do? Well the first line sets up a variable named $expire which holds the value of the date two months from today using some basic maths. Then we use the PHP function setcookie() to create a cookie in the format setcookie(name,value>,expiry date,directory) – now you might be wondering what that final “directory” bit is about – put simply that is the location where your cookie can be read from – if you leave out this parameter you won’t be able to access your cookie, except from the cookie.php page you created it on – not ideal.

Now we have a good thing going now, but we need to think about when the user has submitted the form, and posted an article – we need to alter the cookie to tell our site that the user has used up the token he bought – simply by using the same JavaScript code that we used above, but changing “cval=true” to “cval=false”. Now if you submit your main form using AJAX you can simply add this function in the success: parameter, otherwise you might want to do any number of other things – using jQuery’s submit() function like so.

$("#myform").submit(function(){
  var dataString = "cval=false";
  $.ajax({
    type: "POST",
    url: "<?php bloginfo('template_url') ?>/scripts/cookie.php",
    data: dataString,
  });
});

Or you could stick the code on the page to which new post data is posted (new-post.php). Either way, you just have to ensure, that when the submit button is clicked – the cookie is set to false.

Now we’ve done nearly everything without having touched PayPal – the subject of the next section of the article; but before we begin I want to eradicate any preconceptions you may have about working with PayPal. Many people think it will be rather difficult to use PayPal in the way I am going to describe – that because you are dealing with people’s money there is a greater margin for error. But this isn’t the case – because at the end of the day, PayPal is the one going all the ground-work, and if it doesn’t like what you are doing – it’s going to tell you, so don’t worry – and just go crazy! So go ahead and replace that comment we created earlier “//User hasn’t paid” with the following code – kindly provided by PayPal.

<form action="https://www.paypal.com/cgi-bin/webscr?return=<?php the_permalink(); ?>&cpp_header_image=http://example.com/myHeaderImage.jpg&cbt=Return and post an article&rm=2" method="post">
<!-- Identify your business so that you can collect the payments. -->
<input type="hidden" name="business" value="name@example.com">

<!-- Specify a Buy Now button. -->
<input type="hidden" name="cmd" value="_xclick">

<!-- Specify details about the item that buyers will purchase. -->
<input type="hidden" name="item_name" value="Job Post Token">
<input type="hidden" name="amount" value="1000"> 
<input type="hidden" name="currency_code" value="USD">

<!-- Display the payment button. -->
<button value="Buy Posting Token"><span>Buy Posting Token</span></button>
<img alt="" border="0" width="1" height="1" src="https://www.paypal.com/en_US/i/scr/pixel.gif" >
</form>

So above, we have a form with a heck of a lot of information in it, but if we break it down, it’s actually rather simple. Firstly we set up the form and tell it to post to PayPal’s website – we also specify a number of variables to post along with it – the values of which are highlighted in bold. Firstly we have return – where the user will be returned to, once payment has been completed, for this we use the page’s URL, helpfully provided to us by WordPress. Then we send it something called cpp_header_image – a 90x750px image which will be used in the header – using an image of your own will make the user feel more comfortable, and looks more professional. Then a variable called – cbt – which is the text used on the button which will send users back to the return URL specified above. The last variable is to do with PayPal posting values back to our page – including that of the handy payment_status – so don’t change that.

The next value highlighted in bold is an email address – this is where you should enter the email address of the PayPal account holder to which all transactions will be credited. Next is the value “1000” – which is the amount you wish to charge your users to post – in this case $1000 – may be a little pricy – you decide. The currency is also set below and is currently set to US Dollars. PayPal provides a full list of variables for you to use, which is worth checking out for further customisation.

And that, ladies and gentlemen, is that! So now hopefully you can see just how easy it is to integrate PayPal with WordPress. As always if you have any questions/problems with the tutorial, leave a comment and let me know what you think.

Edit
For those of you who wish to make visitors to your site pay per viewing of each post you would need the following code structure alongside the code above.

<?php
if($_POST['payment_status']=="Completed"){
  $paid = true;
}else if($_COOKIE['activeToken']=="true") {
  $paid = true;
}else {
  $paid = false;
}

if($paid){ ?>

// User had paid, therefore enter the WordPress loop for the post

if(have_posts()) : while(have_posts()) : the_post();

//etc

<?php }else { ?>

//User hasn't paid, so display the payment options

<?php } ?>

Check out the codex for more information on the loop.