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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 this movie, we're going to see how to take the single-page form that we were working with earlier and apply everything that we've learned about validations to it. You can think of this movie as also being known as putting everything together. It's the sum total of all that we've worked on. So we have a form and we're going to have validations on that form. As a starting point, let's go with our form single.php file. Let's open that up. Let's do a Save As on it and let's call it Form with Validation. Okay, so I'm going to save that there. The very first thing I want us to do, before we do anything else is jump down here to the action that was submitting to form single, and change that to match form with validation. Right? Otherwise it won't be submitting to itself anymore.
So now we have effectively the same form that submits to itself. So let's add our validations to it. Well the first thing we need to do is we need to require once our validation functions. Validation functions.php we also know we need an errors array initialized. Let's add that to the top and we know that we are going to want to display the errors down here. So after echo message let's also put parenthesis. Echo form errors, remember form errors is defined in my validations functions value.
So that will display the form errors if there are any. This will just set errors and then there are no errors. We don't have any validations actually happening though. They're being defined, we need them to actually take place. So we can use the validation that we had just in the last movie. I'll put it right here. Right before we do this is the actual action. This is the meat of our application, right, the try to login part. Just put a note here this is the try to login. So before we get to that we want to check and make sure that our data is valid. So has presence, username, not has presence then we're going to set an error.
So if an error's set, then we don't want to do this anymore. This step, this try to login should be conditional on that. So if,empty, errors then we'll do all of this try to login business. I'm going to change this, instead of saying there were some errors in the message, let's say username, password do not match. Okay that's a little more descriptive now. That should work for us. The one other change that we need to make sure we make is that has presence wants us to trim these values before we get there.
And it's up to you whether you would trim the password or not, whether you would allow spaces, I'm going to go ahead and do it. So the password can't have spaces at the beginning or the end or they will get trimmed off. So let's try this now. And note here this is our validations, so if the passes validations we'll do the action, if not, we should see an error message. Let's go to Firefox and this page is now going to be called form with validation, singular. There's my form. And let's just try submitting without putting a value in there. Let's hit submit. Oops, undefined variable message. that's because in the case where neither this happens or this happens, message never gets set.
I just need to set message up here. I'll just set it to an empty string, so it's initialized, it will never give me an error now. Let's just try that one more time, I'll just submit it again. There it is, please fix the following errors, user name can't be blank. Let's try submitting a username now. Kevin, submit. Now I get username password do not match. I don't get my validation errors anymore. So there we are. We now have our validations in place on a single form. Now I wanted us to try this in place because when we're working with post values, what's nice is that we have the ability to dynamically pick the string that we're going to look for inside there to assign that key. And that let's us do some nice things, for example, instead of having our validations like this we can have fields required are username and password. The we can actually check for our has_presence by doing a loop. So we can write a loop for each fields required as field and then inside there you move all this code and let's do each and every one value equals and let's make it $ post.
And then the field see what I mean about dynamically being able to specify that key. That's going to be the value. We'll trim it and then we'll ask it has presence of the value. If so well what key do we want to use, we want to use the field. And we can't use username here. Instead we need to provide the field, can't be blank. Which is a little clumsy. It's a little better if we do something like ucfirst to make it uppercase. You can do more elaborate transformations for that if these had underscores in them for example maybe you'd want to replace that with a space or something like that. So now it's going to loop through each one of my fields that I've required and it's going to call this function on it.
Let's save it and give it a shot. We'll come back over here and let's just try submitting it. Password can't be blank. Take out username, username can't be plank, password can't be blank. Right, see how we can use the power of loops along with our has presence function to speed things up. We can do the same thing with the validations working with associative arrays. Here's another one. I'll just paste it in, so you don't have to watch me type it all. So there we go, same thing. Checking the max length, here's the associative array with the key followed by the length that it's allowed to be. So I've got up to 30 for the username, password can only be eight. It's a little bit arbitrary but we're going to take each one of those and if has_max_length fails, then we'll add an error for it. Go up here and let's try it.
Let's try user name Kevin. Password is equal to verylongpassword, submit it. Password is too long is the error that we got. Now if I have this one be blank and I make a verylongpassword, right it combines the two. Username can't be blank, password is too long. Now you can go even farther with this. If you like this looping idea, we can take this whole associative array and let's go back over to our validation functions. And let's drop down, we'll do it right before we get to form errors.
And I'm going to make a new function, which I'm going to call validate_max length and its going to expect an associative array fields with max_lengths. Its the same name that I was using before and I'll just paste in that code from the other page. Uses an associative array field with max_lengths I don't need to find here I need it back over here. Let me just keep it there. And then it's going to loop through each one using fields_with max_length. It's going to go through each of the errors.
The one thing if you want to do this, if you want to wrap this whole thing up into a regular function that you can call. You're going to need to make sure that you have global errors. So that's going to bring in errors into this scope so that we can work with it. So if you're going to use functions and you're going to need to have access to errors you're going to need to bring that in and make sure it has the global scope. So now I'm validate max_length and just simply be called on field with max_length. Let's try that,. Let's go back to Firefox. Reload the page. This is a long password.
And there it is, password is too long. That's doing it by calling this validate max_lengths function. So there's no limit to what you can do with your validation library, to all the things that you can build up and all the ways that you can use it. Use it in the way that's useful to you. The overall point is to understand the flow of how things happen. The data comes in from the user, we're going to clean it up a little bit. We're going to run it through our validations. If it passes the validations, we'll execute one set of actions. If not, we'll do another set of actions.
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