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PHP is a popular, reliable programming language at the foundation of many smart, data-driven websites. This comprehensive course from Kevin Skoglund helps developers learn the basics of PHP (including variables, logical expressions, loops, and functions), understand how to connect PHP to a MySQL database, and gain experience developing a complete web application with site navigation, form validation, and a password-protected admin area. Kevin also covers the basic CRUD routines for updating a database, debugging techniques, and usable user interfaces. Along the way, he provides practical advice, offers examples of best practices, and demonstrates refactoring techniques to improve existing code.
In the last movie, we created a new subject form. That's just an HTML form and it's going to submit to create subject.php. Create subject.php is going to do the form processing. That's what we're going to work on in this movie, is how we process that form. Now what I have in mind for that page is that it won't render any HTML whatsoever. No matter what happens, there will be no HTML, it's PHP only. And at the end it will redirect the user to an appropriate HTML page. So on success, it will redirect them to one place.
On failure it will redirect them somewhere else. Let's try that. So, because we know we're going to be redirecting, let's go ahead and open up functions.php. And let's paste in that redirect to function that we wrote in the earlier chapters. So, redirect to new location, we'll use a header request to set the location and do a redirect. And then exit afterwards. Remember all the things we talked about with headers. We can't send any white space before we make this call or else we have to have output buffering turned on. My output buffering is turned on.
I'll close it up. Let's open up newsubject.php. And let's also open up a new empty file. This is going to be our create subject page. Let's go ahead and do save, create subject.php. It's going to be inside widget corp inside public. That's where we're going to save it. Alright so create subject. That's the page that we're submitting to, we can confirm that right here. Create subject.php. So, this will post that information over here. So, what information do we need on this create_subject page to be able to do form processing? We don't need any of this HTML that we were working with before.
We don't need to even find the selected page or to bring up the header. We do want these. These are going to be the first thing we want, our database connection and our functions. Now, we don't want the footer down here at the bottom. If you remember our footer actually had a little bit of PHP in it, and we do want to get that. So, we go to our footer file, we have this closing the database connection at the end, we're just going to go ahead and be good citizens and have that the end. I'm going to clean this up a little bit, make it smaller, so now it all just fits on a couple of lines.
Okay, so we've now got our database connection, we've got our functions to find, and we're closing the database connection at the end. What we want to do now is process the form. We can cheat by looking back a little bit at what we did when we were working in the sandbox. Let's open our sites folder and sites, sandbox. In particular databases insert, let's open that up, that's where we did some inserting and look at this. We actually did an insert into objects, so that's going to give us our query that we need, and then I also want to look down here at form processing. Form processing.php.
Now notice that the way we detected the form submission, remember this? If is set post submit. So let's grab that. We're going to want that. We're going to check to see whether or not the post has been submitted. And if it has, then we'll do our form processing. If it's not, then we'll do something else. Now remember, this is based on having submit sent with the form. How do we do that. Let's look over here in our sandbox at the form to remind ourselves, input type submit name equals submit.
That's the magic one right there. This is the value is what the button is going to say. Name equals submit is the value that will submitted with the form request. If we don't have that, it submits nothing so its very important. I'm going to copy that. I'm just going to come back over here. And let's look at the form that we had, in Widget Corp for new subject.php. It does not have that, it has the type and it has the value. We need it to also have the name. So super important, name equals submit. We'll save that.
Now it will trigger this action. It'll say okay, this was a post request. And even more than that, it was a post request from the form that has a submit value that got submitted. Now, if we don't get that, that means it probably was a get request. It means that someone went to their web browser and typed in create subject.php and hit Return without submitting a form. We don't want to allow that so if that happens, we're going to say redirect to, and we'll just go back to new subject.php.
This is probably a get request. I'll just make a little note there and so we'll redirect them. Let's try that real quick just to see how that works. We'll go to firefox, here's our new subject page, but let's instead, let's just do a get request by typing create subject.php. We got redirected to new subject. Now if you didn't get redirected, if you got an error instead, it might be because of that white space issue with doing redirects in the header. Go back and review that section and either fix the white space problem, or it may be easier to turn on output buffering.
Alright let's jump back over to our code again, and let's steal all of this that we did here for databases insert. All if it down here, the whole thing. I'm going to copy all that and I'm going to paste it over here. Because that's going to be my form processing. If it's submitted, then process the form. How do we do that? Well, here's the steps. We get our values. Now, we hard coded those before. Then said they normally come from the post request, well now they are going to come from the post.
So, from our super global post, we can ask it for menu name, and we can do the same thing for position and visible. I'm also using typecasting still on these to make sure that position gets turned into an integer. For visible I can turn into an integer or you can turn into a Boolean. Either one is fine, it doesn't matter because what we are going to be submitting to MySQL. In both cases is going to be translated by MySQL, rather type cast by MySQL into a Boolean, so I'm going to leave it just as a simple integer. It'll be zero or one, that's what we are expecting to get back. I've got my mysql real escape string.
We still want that to prevent sql injection, don't need my message about that anymore. We know what we're doing. Don't need that one either. Insert into subjects. These are the three fields we're going to be inserting, so that's all still good. And then we have our MySQL query. That's still fine. If we get a result back, then it's success. Instead of echoing success, though, now, we're going to redirect to. And let's redirect back to, manage content.php, on failure, instead of doing a die, let's also redirect back, in that case, too.
Redirect to, and we'll go back to new subject also. Now it's worth mentioning that a failure here is a pretty catastrophic failure. It means something really went wrong. Because it's not about validations. We're not doing any kind of validating of the data yet. We'll get to that in a minute. We're submitting values to MySQL and MySQL is rejecting them. It's saying for example, that the position couldn't be inserted. And therefore it won't do the insert. Now it's certainly possible to violate the data rules that MySQL has, that we set up. For example, if you told position that it's an integer of type 3. Well then we can only put in positions up to 999. Soon as we try to put in 1000, it's going to reject it. So I just want to be clear about when that would happen. So, before we try this out and submit it, there's one other improvement that I want us to make.
This MySQL real escape string, it's kind of a long function name to have to remember and recall. And you have to remember to provide the connection before you do it. I think we can come up with something that's a little more convenient than that. So, I'm going to open up functions.php. And right after redirect, I'm going to make a new function here. And I'm just going to call it MySQL_prep. You can call it anything you'd like. But the idea here is that, whatever preparation we need for submitting to MySQL, this function will take care of. We'll pass in a string, that's what it's going to expect is a string.
And instead of having this here, we'll put it in here, and instead, we're going to escape this string. We're going to set, though, escaped string. It's going to be what it becomes. And, afterwards we will do return of escaped string. Notice that we have our connection here, so we need to make sure that we have that available to us. We'll bring that in from the global scope. And now, mysql_ prep will do the exact same thing for us.
It'll take care of this business for us. There are a couple advantages. One, if the process of preparing things for MySQL ever changes, then we can just change things in mysql_prep function. For example, if I was using the MySQL adapter, and I wanted to switch to the MySQLi adapter, I'd just change it in one place. All the places in my code where I was doing my preparation, they can stay the same. The other thing, and the main reason I like this, is because now we can come back over here and we can just use mysql_prep and just pass in the string.
Much shorter, much cleaner, still clear what we're trying to do and it just hides all of the mechanics of it away from us. What's also nice, is that I think now instead of having this as a separate line, it's short enough and simple enough, you can just put it up here. When we first bring that value in we'll prepare it for MySQL. So, now it's escaped by the time it's set to menu name and so we're free to use it here inside our query. Okay, so let's try this out. How are we going know if we succeed or if we fail? We're going to know based on whether it redirects to manage content or back to new subject.
That's what going to be our indication. We could say message equals subject creation failed, that's not bad. Let's do the same thing here. Message equals subject created, that'll work. Put a period at the end of both of those. Those would be a nice message to display. However, there's nowhere to display it, we're redirecting. The redirect is a new request, it's a new part of the request response cycle. Remember that, when we talked about redirects? So, this would have to be stored somewhere. We'll look at that in the next movie. For now, let's just test it out and look based on the page that it results in for whether or not it works.
So we'll go back to Firefox. We're on our new subject page, I'll just reload that just to make sure we're still there. Menu name. Let's put in a sample subject. The position, I'm going to put it in as position five. And visible, I'll say yes. Now, note if you did put it in as a different position here, two, three or four, we don't have a mechanism that will reorder the other ones. That's a, a feature, an enhancement you can add later. For right now, the position would just be a duplicate if we put it in as position two we would have two things that had position two. So, we're going to put it in as position five.
So, let's say sample subject, visible yes. Create subject and there we are. We're on our managed content page and it worked and we know that it worked also because here it is. Sample subject, we can see it. It's right here. Now the idea of looking to see what page you are on, to know if you succeeded or not is not great user feedback. It'd be much better if we could have a message like the ones that we had here. Message equals subject created and to be able to display that to the user. To do that we'll have to use what we know about sessions, and we'll look at that in our next movie.
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