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PHP with MySQL Essential Training
Illustration by Don Barnett

Displaying validation errors


From:

PHP with MySQL Essential Training

with Kevin Skoglund

Video: Displaying validation errors

Now that we understand the basics of validations and some of the pitfalls that we can run into. I want us to talk about how we can display validation errors back to the user in a little bit better way than what we've been doing. So when we had our validation.php file you can see that we were just echoing out validation failed. That's all we were doing is just putting validation failed to the screen. That's not particularly useful. It was great for testing but it doesn't really allow us to have something that's user friendly when we start building a full web application. So, let's take that file, and let's just do Save As on it, and let's do validation errors.php.
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  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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PHP with MySQL Essential Training
14h 24m Beginner Jun 04, 2013

Viewers: in countries Watching now:

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.

Topics include:
  • What is PHP?
  • Installing and configuring PHP and MySQL
  • Exploring data types
  • Controlling code with logical expressions and loops
  • Using PHP's built-in functions
  • Writing custom functions
  • Building dynamic webpages
  • Working with forms and form data
  • Using cookies and sessions to store data
  • Connecting to MySQL with PHP
  • Creating and editing database records
  • Building a content management system
  • Adding user authentication
Subjects:
Developer Servers Programming Languages Web Development
Software:
MySQL PHP
Author:
Kevin Skoglund

Displaying validation errors

Now that we understand the basics of validations and some of the pitfalls that we can run into. I want us to talk about how we can display validation errors back to the user in a little bit better way than what we've been doing. So when we had our validation.php file you can see that we were just echoing out validation failed. That's all we were doing is just putting validation failed to the screen. That's not particularly useful. It was great for testing but it doesn't really allow us to have something that's user friendly when we start building a full web application. So, let's take that file, and let's just do Save As on it, and let's do validation errors.php.

We'll keep these same validation errors in here, but what we're going to do is start changing the messages. And what we want to do when someone submits a form is we want to find out all the errors in that data, in other words, we want to let the errors accumulate. We don't want to just let Return back to the user when we find our first error. If they made a mistake in the first name field, we don't want to go back and say, hey fix the first name. And they submit it and we say, oops, gotta fix the last name, then submit it again, right? We don't want to keep that back and forth ping pong going. We want to find out all of the errors, send them back to the user and say, okay, here are the five errors that were with your form, fix them all and send them all back to me again.

That's the better user experience. Best way to do that is to have errors equal an array, and then we can put our errors in this array and let them accumulate. And then once we're done running all of our validations, we can decide what we want to do with it. Just change this up here to validation, errors too just to match alright, so, the way that we'll add an error then, is that if this is not here, if value doesn't have a presence. Let's instead change this line to be errors and then we could just add to the end of it a new message, value can't be blank.

That's it. Now we've added a validation to it. Now in a real form, that wouldn't be value, that would be first name, that would be last name, city state zip. That kind of thing. Right? We've just been working with value here. But let's go ahead and think about this from the point of view of the application that we're eventually going to build. It's very useful instead of just saying that we're going to add to the end a single message that we tie it to the attribute. And we do that by just providing a key for it, so value here is equal to this, so we've now assigned a key and a value pair and made an associative array.

Value is the key, and then this is the message that goes with it. That's great, because then we know what fields these all tie to. We can see the sum total of the errors, see all of the messages. We also know what the errors were related to. So, let's just try that. Let's go back and let's make this not empty for a second. Let's say that it's going to fail validations by having an empty string here. And let me also just jump down here to the bottom where I was doing this with preg-match. And let's just remove that, that code. So, that's not there anymore.

Alright, there we go. So, now let's go back and instead of validations, let's validation errors. Okay. I got no errors here, because I didn't display anything. That's just at the very end here. Let's just do a print r of dollar sign errors, and let's see what we get back. And there it is, value, value can't be blank. So, this raises the issue though, what do we do after we have our errors? Well, we could redirect the user, we could have some PHP code. I'll drop down here. And let's say, if it's not empty then we have a problem. So, if our array is not empty, then we know that we need to do something. So, that could be redirect, redirect two, first page, PHP for example. The only problem with this is that our errors that we just set here would get lost.

They don't survive the redirect. Remember, the redirect makes a new request to the web server. So, this variable will be unset at that point, unless we put them in the get string, for example, on the redirect, put question mark and then errors equal. That's pretty ugly, really don't want to do that. We could store them in cookies or sessions, we haven't talked about that yet, we'll get to that in the next chapter. That is a possibility, but I think instead of doing that, we have a couple of other options. We could instead include the form again, if we're on a two page setup, so we're submitting to another page, well we could include the form again. And that would then have access to our errors variable to display or then if not, we could include success.php.

So, that would show two different pages, from this form processing page. That would work. The other possibility is that we could it on a single page. That's the approach that I'm going to use. I'm just going to take all of this, and let's just comment it out. There we go. And here we go. If, on the same page, if it's not empty, then let's display some stuff. Let's display div class error. Please fix the following errors. And then I use a UL for an un-ordered list. And all the list will list each of the error messages. Key and the error, it's an associative array.

So I'm listing all the messages out, one after another. Let's try that. I'm going to take this print r away. Let's just see how that works. Come back, reload our page. There we go. Please fix the following errors. Value can't be blank. Much more user friendly right? And this can be turned into a function, that's not hard to do. You might want to pause the movie and try it on your own just to see if you can do it. Let's call it form errors and we'll pass it in errors. And the default will be a empty array. And then all of this code will go inside of there. I'll get my indentation right.

But instead of echoing out, I've told you that that's a bad idea. It's much better to do output equals and then output. We'll add that to our output each time. And every time we have an echo, I'm just going to take that output, put that in there instead. And then once it's all done, then we're going to return our output. Turn dollar sign output. Now I see a problem here in my logic, which is the output might not get set. So, I want to start out with an empty $Output, to make sure that it has an initial value of just an empty string.

Okay? So there we go. Now it'll take all that, it'll add it all up, and I can now call it by saying echo form errors, and I'll pass it in my errors string. Try that, go back and reload it. And there we go. So, now I've got a function that's reusable. I can put that in my functions file. And then include it or require it on all different pages. And I'll be able to call for all my form errors. It'll loop through each and every one of the errors, one after another, and report them back to the user. And this is the process that we'll go through when we build a web application. Now you could go even further with this.

You could have the array key exists function, to find out if a key exists in that errors array. So, if for example the name field had a problem, we could look for that key. If there's a message associated with it, we'll find a key there. So, if we find that the key for name inside the errors, then we could output something, maybe it puts little arrows, that's what I've done here. Little arrows that might go next to the field, showing that there's an error there or maybe it adds a class to the field itself, so that it can be displayed. And read, or have a red border around it, something like that.

This level is customization really is up to you. The main thing is that I want you to understand the basic idea of how we're letting these errors accumulate. And then we want to display them all back to the user at the same time, in a nice, user friendly way.

Find answers to the most frequently asked questions about PHP with MySQL Essential Training.


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Q: This course was revised on 6/4/2013. What changed?
A: The old version of this course was 6 years old and it was time for a complete revision, using PHP 5.4. (The tutorials will work with any version of PHP and covers any differences you might encounter). The author has also added updated installation instructions for Mac OS X Mountain Lion and Windows 8. The topics and end project are the same, but the code is slightly different. It also addresses frequently asked questions from the previous version.
 
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