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Custom validation functions

From: PHP with MySQL Essential Training

Video: Custom validation functions

Over the last few movies, we've seen how to validate the form data that comes in to us and how to display useful error messages back to our user. But our validations right now are not really reusable, we've just written if statements. If a certain logic is true or if a certain logic is false, then add an error. It would be much better if we could take that validation and put it into a custom function so that we could reuse it. And that way, every time throughout our entire application that we want to check and see is a form field blank, we can just call our function and ask it. Hey, use your logic that you have built in and tell me, is this form field blank? What's going to be really useful, is if we can develop a file that is going to be a library of validation functions that we can just include and call upon whenever needed.

Custom validation functions

Over the last few movies, we've seen how to validate the form data that comes in to us and how to display useful error messages back to our user. But our validations right now are not really reusable, we've just written if statements. If a certain logic is true or if a certain logic is false, then add an error. It would be much better if we could take that validation and put it into a custom function so that we could reuse it. And that way, every time throughout our entire application that we want to check and see is a form field blank, we can just call our function and ask it. Hey, use your logic that you have built in and tell me, is this form field blank? What's going to be really useful, is if we can develop a file that is going to be a library of validation functions that we can just include and call upon whenever needed.

That way, we can do it throughout our application, and potentially we can even take that file from project to project, and always have these validations ready for us to call. It's very handy. Let's see how to create that kind of file now. So to begin with, let's open up our validations.php that we worked with before, that has all of the logic in it that we want. And let's do a Save As on this, and instead of validations, we're going to call it validationfunction.php. Now its not going to have any HTML in it anymore its just going to be PHP that defines our function. So we want to take the HTML out of the top and bottom, and I'm also going to take out some of these that I'm not going to use.

So I'm going to take out uniqueness, and format, I'll leave inclusion in, I'll take type out, and let's take minimum length out as well. Now, you can do all of these on your own. I'm only going to show you this subset, just these three as an example. So for all of these, I'm just going to take the indenting out. And then let's change each one of these to be a function that's reusable. So instead of having a value set here, what I want to have is a function whose name I'll call has presence, and it's going to accept a value as an argument. So, all this logic is going to come up inside here, but there are a couple of differences, some changes I need to make.

First of all, I don't want it to echo anything back. So I'm going to take that away. What I want it to do is return true or false, so I don't need this if statement at all. And I can actually take the parentheses away. This is now a Boolean, the result of this will be either true or false. We saw that when we worked with Booleans before. But in addition, I need to make sure since it's in our function, that I call return on it, so that it is returned back as a value. Now, if I call has presence and I pass in a value, it'll return back true or false to me. But, the logic that I had worked on before, was actually if it was false, then add the error.

But has presence is the opposite. It's not has no presence, it's has presence. So I need to reverse the logic of this. I think it works better if these work in the affirmative instead of the negative. So if it has the presence, it will return true. So, I have to reverse each one of these, is set, and (INAUDIBLE) value is not exactly equal to an empty string. See how that works? So if it is set and the value is not equal to string, then it has presence. True. If not, it would return false. Alright, so let's look at the next one. Let's say that we have string length, maximum length, instead of having max, instead I'm going to have a function has max length. And it will return true or false, once again, based on whether or not it has this maximum length.

Now, it's a little bit awkward naming, maybe you want to name it something else. But to me it means that it is under this maximum length. So, let's make those same changes we made before. Take that out and that out, return the value and now I just need to reverse the logic of it. So, now it's not less than, but less than or equal to. Be careful when you're working with less than and greater than, that you consider that equal to case as well. So if the string length is less than or equal to the max then true, it has a maximum length of whatever we've asked it for.

Alright, let's try another one. Let's do inclusion in a set, take these away, function has_inclusion_in, and I'll pass it $value and $set. Alright? Now, I know I don't need all of this anymore. I just need this bit of logic in the middle. Return. And I need to reverse the logic so that if it's in the array, it returns true. So it has inclusion is basically the same thing as saying in array. This just makes it a little more feel like a validation, and this just happens to be the way that it's going about it.

Might be also that you beef up this function over time so that it does other things. So I don't mind it. Okay. So now that we have our little mini validation functions file, let's include some of those and start trying them out. So, I'm going to go over to Validation errors, and the very first thing I'm want to do is go to the bottom of it. You'll see that we had form errors, that was a function that we wrote before. Let's reuse that. Let's just grab that. I'm going to cut it, I'm going to add it to my validations function. So now it's here as well. So that'll get defined at the same time. So I don't need it here. I can take out a bit of this PHP.

I don't need any of these validations that I was doing before, because all of these now can be handled with require-once and validation-functions.php. So there we go. I still have my errors the way that's being set, and then I'm displaying any errors that came up. So, if we were working with a real form, we would probably be checking to see if the post variable had been set. We would be then pulling in the value something like this. For now, just for demo purposes, I'm just going to set username right here in the file.

So if username is equal to trim and we'll put in an empty string, then we'll check if not has presence calling our new function on username. And then we can define our custom behavior, whether we want it to do. We might not want it to do the same thing every time we call the function. We'll call it user name equals and let's say, user name can't be blank. Pretty standard stuff. Alright, so then we'll display that. Our user name is blank, so we should be able to see that page if we go to validationerrors.php.

Validationerrors.php, it's where we're working at before. Reload the page, and there we are. User name can't be blank. If we test it, move that out of the way. Where's the other file? There it is. User name is Kevin. Now we try it, and it doesn't give us an error anymore. See how that works? Now we have some reusable functions that we can use each and every time. So now that we know how to create validations and we've made them into reusable functions, let's try putting it all together by applying validations to our single page form submission.

We'll do that in the next movie.

Show transcript

This video is part of

Image for PHP with MySQL Essential Training
PHP with MySQL Essential Training

131 video lessons · 36043 viewers

Kevin Skoglund
Author

 
Expand all | Collapse all
  1. 4m 8s
    1. Welcome
      1m 0s
    2. Using the exercise files
      3m 8s
  2. 15m 6s
    1. What is PHP?
      3m 52s
    2. The history of PHP
      2m 51s
    3. Why choose PHP?
      4m 10s
    4. Installation overview
      4m 13s
  3. 54m 53s
    1. Overview
      2m 33s
    2. Working with Apache Web Server
      6m 56s
    3. Changing the document root
      7m 24s
    4. Enabling PHP
      6m 16s
    5. Upgrading PHP
      3m 30s
    6. Configuring PHP
      10m 3s
    7. Installing MySQL
      5m 46s
    8. Configuring MySQL
      7m 24s
    9. Text editor
      5m 1s
  4. 31m 25s
    1. Overview
      3m 27s
    2. Installing WampServer
      5m 46s
    3. Finding the document root
      2m 24s
    4. Configuring PHP
      8m 12s
    5. Configuring MySQL
      5m 45s
    6. Text editor
      5m 51s
  5. 19m 12s
    1. Embedding PHP code on a page
      6m 43s
    2. Outputting dynamic text
      5m 55s
    3. The operational trail
      2m 27s
    4. Inserting code comments
      4m 7s
  6. 1h 18m
    1. Variables
      7m 50s
    2. Strings
      4m 38s
    3. String functions
      8m 54s
    4. Numbers part one: Integers
      6m 27s
    5. Numbers part two: Floating points
      5m 25s
    6. Arrays
      10m 0s
    7. Associative arrays
      6m 37s
    8. Array functions
      6m 33s
    9. Booleans
      3m 50s
    10. NULL and empty
      5m 15s
    11. Type juggling and casting
      8m 27s
    12. Constants
      4m 43s
  7. 27m 37s
    1. If statements
      6m 0s
    2. Else and elseif statements
      4m 16s
    3. Logical operators
      7m 30s
    4. Switch statements
      9m 51s
  8. 42m 15s
    1. While loops
      8m 41s
    2. For loops
      5m 59s
    3. Foreach loops
      8m 16s
    4. Continue
      8m 28s
    5. Break
      4m 8s
    6. Understanding array pointers
      6m 43s
  9. 37m 25s
    1. Defining functions
      8m 25s
    2. Function arguments
      5m 32s
    3. Returning values from a function
      7m 33s
    4. Multiple return values
      4m 53s
    5. Scope and global variables
      6m 2s
    6. Setting default argument values
      5m 0s
  10. 20m 18s
    1. Common problems
      3m 47s
    2. Warnings and errors
      8m 36s
    3. Debugging and troubleshooting
      7m 55s
  11. 57m 57s
    1. Links and URLs
      5m 33s
    2. Using GET values
      5m 35s
    3. Encoding GET values
      8m 41s
    4. Encoding for HTML
      9m 26s
    5. Including and requiring files
      7m 40s
    6. Modifying headers
      6m 45s
    7. Page redirection
      6m 43s
    8. Output buffering
      7m 34s
  12. 1h 3m
    1. Building forms
      7m 28s
    2. Detecting form submissions
      5m 59s
    3. Single-page form processing
      7m 57s
    4. Validating form values
      10m 40s
    5. Problems with validation logic
      9m 54s
    6. Displaying validation errors
      7m 23s
    7. Custom validation functions
      6m 28s
    8. Single-page form with validations
      7m 25s
  13. 28m 5s
    1. Working with cookies
      2m 49s
    2. Setting cookie values
      5m 55s
    3. Reading cookie values
      6m 1s
    4. Unsetting cookie values
      4m 51s
    5. Working with sessions
      8m 29s
  14. 48m 39s
    1. MySQL introduction
      6m 43s
    2. Creating a database
      7m 41s
    3. Creating a database table
      7m 42s
    4. CRUD in MySQL
      5m 48s
    5. Populating a MySQL database
      7m 32s
    6. Relational database tables
      6m 40s
    7. Populating the relational table
      6m 33s
  15. 56m 4s
    1. Database APIs in PHP
      4m 51s
    2. Connecting to MySQL with PHP
      7m 45s
    3. Retrieving data from MySQL
      8m 47s
    4. Working with retrieved data
      6m 12s
    5. Creating records with PHP
      6m 58s
    6. Updating and deleting records with PHP
      9m 6s
    7. SQL injection
      3m 5s
    8. Escaping strings for MySQL
      6m 45s
    9. Introducing prepared statements
      2m 35s
  16. 35m 58s
    1. Blueprinting the application
      7m 19s
    2. Building the CMS database
      5m 14s
    3. Establishing your work area
      4m 38s
    4. Creating and styling the first page
      4m 22s
    5. Making page assets reusable
      6m 36s
    6. Connecting the application to the database
      7m 49s
  17. 32m 49s
    1. Adding pages to the navigation subjects
      5m 58s
    2. Refactoring the navigation
      6m 7s
    3. Selecting pages from the navigation
      6m 2s
    4. Highlighting the current page
      5m 26s
    5. Moving the navigation to a function
      9m 16s
  18. 1h 45m
    1. Finding a subject in the database
      9m 48s
    2. Refactoring the page selection
      10m 52s
    3. Creating a new subject form
      6m 55s
    4. Processing form values and adding subjects
      11m 20s
    5. Passing data in the session
      9m 16s
    6. Validating form values
      9m 40s
    7. Creating an edit subject form
      8m 30s
    8. Using single-page submission
      7m 44s
    9. Deleting a subject
      9m 44s
    10. Cleaning up
      10m 37s
    11. Assignment: Pages CRUD
      4m 30s
    12. Assignment results: Pages CRUD
      6m 10s
  19. 39m 26s
    1. The public appearance
      8m 52s
    2. Using a context for conditional code
      11m 37s
    3. Adding a default subject behavior
      6m 9s
    4. The public content area
      5m 51s
    5. Protecting page visibility
      6m 57s
  20. 1h 3m
    1. User authentication overview
      4m 3s
    2. Admin CRUD
      8m 41s
    3. Encrypting passwords
      7m 26s
    4. Salting passwords
      5m 42s
    5. Adding password encryption to CMS
      11m 54s
    6. New PHP password functions
      3m 13s
    7. Creating a login system
      11m 28s
    8. Checking for authorization
      5m 48s
    9. Creating a logout page
      5m 40s
  21. 2m 4s
    1. Next steps
      2m 4s

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