PHP with MySQL Essential Training
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Refactoring the page selection


PHP with MySQL Essential Training

with Kevin Skoglund

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Video: Refactoring the page selection

At the end of the last movie I gave you an assignment to try for yourself. That is to take everything that we learned about find subject by ID and to create your own version of find page ID. Hopefully that went well for you. We'll take a look at the results to make sure that we have the same thing and then we'll talk about how we can refactor the page selection. So the first thing we're going to look at is functions.php and I've got find_page_by_id. It's a pretty simple function for you to create because you can actually just take find_subject_by_id. Copy it and then just change every instance of the word subject to say page instead.It's exactly the same thing. And in fact this is the same thing that you use every time you want to read back a single record from the database.
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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. 1h 3m
    1. Overview
      2m 33s
    2. Working with Apache Web Server
      6m 56s
    3. Changing the document root
      7m 24s
    4. Installing to Yosemite NEW
      8m 13s
    5. Enabling PHP
      6m 16s
    6. Upgrading PHP
      3m 30s
    7. Configuring PHP
      10m 3s
    8. Installing MySQL
      5m 46s
    9. Configuring MySQL
      7m 24s
    10. 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 from
14h 24m Beginner Jun 04, 2013 Updated May 20, 2015

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
Kevin Skoglund

Refactoring the page selection

At the end of the last movie I gave you an assignment to try for yourself. That is to take everything that we learned about find subject by ID and to create your own version of find page ID. Hopefully that went well for you. We'll take a look at the results to make sure that we have the same thing and then we'll talk about how we can refactor the page selection. So the first thing we're going to look at is functions.php and I've got find_page_by_id. It's a pretty simple function for you to create because you can actually just take find_subject_by_id. Copy it and then just change every instance of the word subject to say page instead.It's exactly the same thing. And in fact this is the same thing that you use every time you want to read back a single record from the database.

Find whatever it is by ID. It's going to look very similar to this. So this is a good template to keep around and reuse. If you don't have the same thing as me, go ahead and pause the movie and you can copy all of this down. I'm going to go ahead and move over to manage content.php. Where I've also done some copy and pasting. I took my current subject, and menu name display, and I used it down here as current_page. Again, just swapping in every time I see subject, swapping in page. I took one additional step. I moved the H2 inside my if statement, so that it can be conditional as well. Instead of just saying manage_content, it now says manage_subject or manage page. I thought that was a useful improvement, because otherwise, as I click around, I don't know whether I'm on a subject or a page.

Menu name doesn't give that away. Menu name is the same for both. So now, we can tell whether we're looking at a page or a subject. Okay so again, you can pause the movie and copy that down if you need to. But we're not ready to talk about how we can re-factor this. So, one of the first things that I noticed about this is just that there's a lot of code up here for selecting the page. And the more code that's down here for selecting the page. And I think we can clean up the relationship between those two a little bit. The first thing I notice is that I'm doing this setting of current subject here.

I'm doing it as I am about to use it. I like to do these finding and setting up of variables as early on the page as possible to get them set up. And to keep them out of the display or presentation of the information. So if possible, it's not always possible sometimes we are inside of a loop and we have to do it down there. So when possible I'm going to put it up here instead, This is the same conditional statement, right? I'm checking to see if the subject is set. If its set, then let's set select subject ID. And let's find the current subject. Let's jump back down here.

We can do the same thing for page, remove all of that. I'll put this up at the top. We will select our page ID. And then we'll set current page right afterwards. Now, I think that's an improvement. I think it's a little cleaner down here. We're just dealing with the display of these different things. Now, I also noticed, though, that selected subject ID used to make a lot of sense before. Right? We were checking to see for the presence of selected subject ID, but we're really just working with current subject. Why can't we just check for that? Right? Current subject is either going to exist or it's going to be null. So let's use that instead.

So if it's null, then this Boolean will evaluate the false. Now you could use is null, or if not is null is there, but this works just the same. This Boolean expression if we have a current subject, then do this. If we have a current page, then do that. The only problem is we need to watch for our default values. Because here we have a subject we want to make sure that we still also have a current page set. Null, and let's do the same thing for current subject, equals null.

And here as well. Then do current subject equals null or current page equals null. Okay, so now we've cleaned all that up and now it should still work. Let's just make sure our refractors still work. We reload the page, we click around and nothing has changed. Okay, so that's a good refractor. So this, to me, looks a little cleaner down here now. But I've kind of made a mess up here at the top. This is a, a big jumble now.

At least I'm doing it all in one place. But I think it can be cleaned up a little bit. And I'm noticing, for example, that I'm setting selected_subject_id here so that I can just reuse it here. Why not just use this value? The only other time that I'm using selected subject ID is down here in the navigation. We'll get to that in just a second. For now, let's go ahead and just take this and let's replace it. Let's say, alright, we're going to use that there instead and we'll do the same thing here with selected page ID. Now we're on the way to actually getting rid of selected subject ID and selected page ID. Get rid of those.

Right? So it just goes directly to it. Just take this value, send it in here. It's going to do MySQL real escape string, so we don't need to worry about the safety of it or anything like that, it's going to get escaped. So now we're going to just have either a current subject or a current page. This will work except for the navigation. Let's just comment out our navigation for a second and let's just try it. Let's come back over here and let's reload the page. You see that it works with page one, page three or subject three.

Right? I'm just typing it into the url up here since I don't have a navigation. Problem is, when we add the navigation to it, this is navigation wants these IDs. So, how can we set up an ID? Well, we could just send it this same value. We could say, let's drop that in, get subject, get page. Right. There we go. That should work right. We're just sending those same values into navigation. Let's reload the page. Whoa, wait a minute. Notice here I get a warning that something hasn't been initialized, that's because one of these values doesn't exist.

At the moment, I'm on a subject page so Get_page doesn't exist. It goes to look for, and it's not there. We've moved outside of this very important is set, checking to see if it is set or not. So we don't want to do that, we want to stay inside of this is set. So what could we do instead? Well we could send current_page. We could say current_page and it should then have an ID, right? And same thing for current_subject. Now we're going to have the same problem.

In some cases current subject is going to exist and some pages current page is going to exist, but they're not going to exist at the same time. Now we actually might be able to call a key on null and have it not blowup on us. But that's beside the point, it's really not a good programming practice. Instead, let's just pass in the current_subject and the current_page. Whatever they maybe, they maybe an associated array or it maybe null, and we'll just handle it inside navigation. Navigation will expect to get one or the other. It will either expect an associative array or it will expect null.

Let's just close that up. Let's go back over to our functions and make that change. So now, instead of navigation taking two arguments. The currently selected subject_id, we're going to say the current_subject array or null and this one will be the current page array or null. And then let's make that change here. So that we're expecting either a subject or a page. And then just here, we just have to check, right? We may be getting back a subject, which we can call ID on. Or we may be getting a page that we can call ID on. However, we might not, we might be getting null. So let's just add an additional condition here.

That says, if subject and subject id is equal to subjects. So if we have a subject, and if the subject id is equal to subject id, now notice what we just did here. This should be a subject array, and page array, to keep them separate from what we're using inside our loop. Alright. And down here, call this one page array and we'll just check also for page array being present.

So if we have a page_array and page_id is equal to page_array's ID. Alright a little cleaner let's take a look and see if it works still. Come back here and reload our page there we go. Now we are clicking around and we are getting the same results. We have made things different in our code but the functionality is the same that's what we want to do when we are re factoring. I find this all to be a little cleaner and easier to use. Let's do one last re factor here before we leave this. I'm just going to take all of this and I'm going to cut it, take it out, I'm going to go back to my functions.php and I'm going to make a new function for it.

So, let me just take find navigation and right below it, let's, right here, let's do function find selected page. It's not going to take any arguments because it is going to use GET, and then it's going to set values based on that. This is a super global, it's available everywhere. We don't have to call global scope on it. So find_selected_page is all we're going to have to call now from over here, and it's going to do all that work for us.

All right so we just wrapped it all up. We don't need to echo it or anything. We just need to tell it to find selected page and what that's going to do is set values for us for current page. Let's come back over here. There's one issue though. We need to return either current page and current subject. Right, we can do that down here. Return. We can return the array and then catch those values. Or we can just declare them as being global. That will essentially say that these are in the global scope, that that's where we're working on them from, global subject, and current page.

Even though they didn't exist before they got here, it's okay, we're creating them in the global scope. We're referring to them in the global scope. So here when they get defined It's the global scope where we're using them and that means that they're still available to us once we leave the function. So let's just close all that up now. And let me just put a return here so that separates it. Let's go back over to Firefox. Let's reload the page, let's click around and everything still works as expected. Notice how much cleaner that is? All of that business gets taken care of here in this function, and we can really focus on just the display here, really just focus on that aspect of it. The presentation of the data that we've already set up. I think this is a real improvement.

Okay. Now that we have our subject and page reading down, we're ready to move on to the next part of CRUD, which is create.

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.
Q: This course was updated on 5/20/2015. What changed?
A: We added one movie called "Changing the document root in Yosemite," which helps the Mac installation run more smoothly.
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