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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.
It's time for us to add some form validations to our create subject form. Right now, we're not performing any validation, so we need to add them. And we talked extensively about how to write validations earlier, so we're not going to be doing a lot of that. We're mostly going to just be looking at how we can install them in our application, and use them effectively, as well as how to put the error messages in the session. Now you remember that in the validation section, we came up with a file called validationfunctions.php, and it was the beginning of a collection of validation functions that we could start to use and reuse.
We're going to pull that up, and we're going to use it again here. So I'm just going to copy that, and I'm going to make a new file, New, Paste it in. This is just all the contents of that, we're going to save it inside Widget Corp, inside includes and I'm going to call it validation_functions.php; same name. And we could put it in our regular functions file, but I'm thinking that it's nicer to have it as a seperate file, because then we only have to load it when we need it. We only call those validation functions and bring them into memory, and have them available to us when we have a form.
Otherwise, we don't bother. We don't take up any space or anything in PHP by loading those unnecessarily. So it's nice to be able to, to load them selectively. Okay, we can close up our sandbox now. And inside validation functions, I'd just want to make a couple of additions. You remember that we made a change here, where we said, validate max lengths is going to go through an associative array and run, has max length for each and every one. Right, that was the function that we created. I'm just going to take that, and I just move it up so that it's right under has max lengths, I think that makes more sense, so they're right there together.
And then has presence, right now, we were just calling as a single item. We were just calling has presence one time, but I want to also make that into a loop as well with validate presences. So, that'll take an array and then loop through the array calling has presence on each one. If it does not have presence, then it'll put an error in there. Now, we can also go ahead and make sure that we always have and errors array to work with. If we load up our validations, then we can have it go ahead and create errors equal array, and that will make sure that we always have errors ready to go. Right, we don't have to remember to initialize it. Just by loading in our validationfunctions.php, by including or requiring that, we're going to get our errors array ready to go. There's another change that I want us to make.
You'll notice that in my error messages, I've got ucfirst, that's going to upper case the first letter of the field and say it can't be blank. But one of the items we have is menu name, so that's going to result in something that says uppercase Menu_name. That's not so great. It's a little more user friendly if we can get rid of that underscore. So I'm actually going to paste in a new function here. going to put it up above all of these, and it's going to be called field name as text. And it's just going to take the name of a field. It's going to replace, using string replace, all underscores with spaces, and then call ucfirst on it. That's a little bit of an improvement, so we can just use that instead. Field name is text.
Field name is text. So there we go. Alright, so now we've got our validation functions, let's use them. Let's close that up, and let's open up createsubject.php, that's our form processing page. And we're going to want to have not just our functions, we're going to want to make sure that we have our validation functions, right. So now those validation functions are going to be loaded in, the errors array will be initialized for us and we're ready to go through it and perform some validations. Now, we want to perform the validations if POST has been submitted. We want to do it before we actually do our insert.
Now, you can do it either up above these values or below them, it's really up to you. I'm going to put them right here in the middle. So right here is where I'm going to do validations. And for the validations that we're going to run, I'm going to do required fields. And what fields are required to have values here? I'm going to say that all three of them have to be provided to us. So it's going to be an array of menu_name, position and visible. Alright. So now, we have our required fields, that's defined. Now, we need to call our validate_presences on required_fields. Okay? So we defined it here just so it's nice and easy to see, and then we're calling that loop on it. And that loop will have the effect of putting errors in for anything that has an error.
So, we'll end up with errors if something is not required. Let's do the same thing with fields with max lengths. We saw that before, there is one that we actually did previously. So I'm going to say my fields with max lengths are going to be menu_name. It can only be 30. That's the maximum length of the menu name. We'll call validate_max_lengths on that. And you can certainly run a lot more validations than what I do here. This is just meant to give you a sample of some of the main ones. The pen, once we're done running these validations, we want to check and see whether we had any errors. We don't want to run this statement unless we didn't.
So how do we check that? We say if, not empty, and errors. So if its not empty, then we're going to store those errors in the session that we have access to them, and we're going to redirect, redirect to new subject.php. Now you can just let this redirect happen on its own like this, or you can actually do else, and then inside this block, put all of this code in there.
That's really up to you, whether you want to, to nest that each of those additional times. But this redirect will immediately redirect so that it won't actually call anything additional. And that's because that redirect tool had an exit after it. So, that's enough to do it. So, let's redirect to and then exit, will keep anything else from running. So let's try it. Let's see if this works on it's own. Just to find the errors, mark them and keep the insertion from happening. We don't have anything that will read the errors yet, we'll work on that next. Let's go to Firefox. We're on our new subject page, let's reload it. Don't get any errors yet, that's good.
It means it loaded in all our functions correctly. And let's just try doing Create Subject. And you see that it'll just go back to the new subject page. Alright. I'm back on new subject each time, you can see it very quickly flicker as it goes to the other page and, and reload. So that's how fast a redirect actually happens. So now we need to read those errors back in. So that's not on the Create Subject page, that's just processing. We want to actually display them on the form itself. So, newsubject.php. We don't need to include our validation functions here, because those are just performing the validations. Right? We don't need to initialize errors or anything like that. What we need to do is get back the errors that were in this session. So, why don't we go into session.php, and let's write something similar to what we had for message here, but that returns what was in the errors. We'll say errors, and I'll just take that and swap it in. But instead of returning something that's formatted in HTML because I don't really need it that way, instead we're just going to see errors equal to, you don't need HTML entites on that.
you could call it I guess, but I'm going to say that the errors, you know, don't come from the user, it's not going to be something that's going to have user data. This is data that I'm putting in control of. And then we'll clear the message after we do it, and we'll return errors. It's a little bit simpler, we don't have any HTML around it, we're just basically getting the errors, clearing them and returning them. So then we can call this, and that will have the effect of finding our errors and clearing them for us. That's nice. So let's save it, let's go back over here and we can put our errors absolutely anywhere that I want. Let's say that we'll do it right below the message for now. So PHP, I'm going to get our errors, that's going to be equal to errors, and then once we have that then we'll just output them. And we had a function that we wrote that would output them, that's also in my validation functions.
Here it is, form errors. That's probably a good candidate to move out of validation functions so that I have access to it. Right? because I want it when I don't have validations. So, I'm going to cut that one out of there, and put it in my general functions. So here, my general functions and I'll put it right here after confirm query, that's a good spot for it. So now I have access to it all the time, and so we can just call forum errors and we'll pass it errors, and we gotta make sure that we echo that back. It needs to have an echo.
Alright? So let's try it all now. Let's go back over here, and let's hit Create Subject. Please fix the following errors, menu can't be blank, visible can't be blank. Alright? If we go through and we put in something for the menu name, create subject, now it says visible can't be blank. If we put in something that's much longer here, I'm just going to type a whole bunch of x's, let's say See if I can do more than 30, I may have told the field not to let it be that. Yeah, menu name is too long, so you get that error as well. So that's it, now we've installed our validations. And we've got our validations, so that they are able to store the errors into the session and then after we redirect, we're able to pull them back out and display them to the user. Now you could write something a lot fancier than this, you could write something that would first of all display them a little nicer, make it look a little better.
But we also could have it so that it would highlight fields. It would say oh, there was an error on menu name, I see that key in there, well, let's put a red border around menu name so that the user knows exactly which field needs to be fixed. Those kinds of things I'll leave to you as an exercise, the main thing that I wanted you to see was just how we install and run our validations. And how we get errors across the redirect so that we can display them to users.
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