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Connecting the application to the database

From: PHP with MySQL Essential Training

Video: Connecting the application to the database

In this movie, we're going to use what we've learned about database connectivity in our application to connect to the database. And then create a list of subjects on manage content.php. We're going to start by just listing all of the subjects. In the next chapter, we'll add pages to it and see how to bring up page content. So go back and review database connectivity if you need a refresher. Remember there's five steps that we need to follow. We're going to create a database connection, form our database query, use the returned data if any. Release the returned data, and then close the database connection. Let's start by opening up that file that we worked with earlier. That's inside our Sights folder, inside Sandbox and it's called databases.php. Let's just open that up for reference.

Connecting the application to the database

In this movie, we're going to use what we've learned about database connectivity in our application to connect to the database. And then create a list of subjects on manage content.php. We're going to start by just listing all of the subjects. In the next chapter, we'll add pages to it and see how to bring up page content. So go back and review database connectivity if you need a refresher. Remember there's five steps that we need to follow. We're going to create a database connection, form our database query, use the returned data if any. Release the returned data, and then close the database connection. Let's start by opening up that file that we worked with earlier. That's inside our Sights folder, inside Sandbox and it's called databases.php. Let's just open that up for reference.

This has all of that connection in there, and we can just copy this over. We're going to add it to our managedcontent.php page, so let's add it right here before we even do the functions. Let's do it right at the very beginning, and we're just going to grab all of this PHP here for step 1, which is create a database connection. So just copy that, let's bring it over and paste it in. So now this will create our connection and it will test to see, was there an error. If there was an error the database connection will fail. Then the second thing is to perform a database query.

Let's do that as well but let's don't put that block here at the very top, let's do that one after we've done our functions. Before we start actually doing the layout we're going to do it right here, we're going to perform our database query. And then, let's drop down here to use return data if any, and it just so happens we were working with subjects before. That's what we were bringing back was displaying a list of the subject. Is perfectly appropriate for use to still use, make sure that you get the UL tags that go with it we'll copy that. And where we want to put this is inside the navigation. So inside the navigation, instead of that nbsp, we want to get rid of that and instead use the return data.

That's going to be our list inside the navigation. And then, release the return data. We'll do that after we're done with it so, let's do it right here after Main. Right before we do our footer, we'll release the data that we were working with. And then last of all, close the database connection. And that can be the very last thing that we do down here after the footer. So, that's it. We just basically imported all of this code that we were working with before from just a very simple framework. We brought it all over so that we can work with it here in ManageContent.php.

Let's bring it up and try it out. So, we'll go into Firefox. Here's my Manage Content page. I'll just hit Reload and there we go. About Widget corp and then it still shows the IDs after it in parentheses. That's fine for now. Go ahead and leave those. We can always remove them when we're finally done with it. Now, I'm also going to do one more thing to this, which is just to the UL, I'm going to give it a class of subjects. And that's going to make some style kick in for that, which will make it a little cleaner. It will just bring it over a little bit to the left. So, now that we have it working on this page. Let's improve it using what we learned in the last movie about making reusable assets for ourselves. Let's move our database connectivity to a file in the includes directory. So let's create a new file for ourselves, and let's just move some of this code over there.

What I want to do is move the database connection, which happens right here at the top. I want to take that out of here, cut it, i'm going to paste it in over here. And I'm going to save this as Save, Inside Widget Corp, inside includes and I'm going to call it db_connection.php. There we go. Now I can come back over here. And I will use require _once instead of Include. I'll use require_once. And instead of Functions, it's db_connection.

So now, all I have to do is make this line and voila, I've got a database connection. It's that easy. If some configuration changes about my database connection, I can come in here and it'll change it for my entire website. It's nice, huh? Alright, so let's close that up. Now notice here, the database query is unique to this page, though. At least for the moment. We'll come back to that and make improvements on it later. But for the most part, it's going to be unique to this page. Using the return data is unique to this page. And freeing the result I would say is also part of this page. You don't have to. You could move freeing the result to something at the end. It could happen for example in the footer, but then you always have to call your result, result.

And I like the fact that it bookends the query that I made up here. So I do a query up here, and I can see that I freed the result down here. However, closing the database connection can be moved somewhere else. And you could move it to a file called db_connection_close. And always have that at the one. But I also think that we can just take it, and we can move it into our footer. So lets close that up, and lets find our footer file. So we can just put it right here at the bottom of our footer. So once we're done with our HTML, the very last thing we can do is close the connection.

Now you don't actually have to close the connection, PHP figures it out if it gets to the end of the page and it's done and it still got this connection open. It says oh yeah, I guess I'd better close that. If no one else is going to bother doing it, I'll do it. So it will do it, but it's still a good practice to put it here. Now, because we might be using this footer on pages that are not database enabled, places where we did not ever open a connection. It's also a good practice to check and see whether a connection has been set before we start trying to close it. So let's just add a little statement here, if is set, connection, so if it's set, then close it.

And that's a little better. So now, if it's there, close it by the time you get to the end of the page. Because once we're done with our HTML, we probably don't need that database connection anymore. So, now if we go back to Manage_content.php, you can see that once again, we've slimmed down the page, quite a bit. By taking out all that database connectivity and putting it somewhere else. There's one more change that I want to make here. Notice that we tested that there was a query error and so, on every single page, I'm going to have this bit of code. Checking to see, did I get back a failed result. This is a perfect candidate for moving to a function, that's exactly what I'm going to do. I'm going to open up that functions.php, and I'm going to just write my first function here in this file.

Function, I'm going to call it confirm_query, and it's going to take, I'll call it result_set, instead of just simply result. And if there's not a result set. Then, let me just grab that same behavior we had the die, that's what I want. The die with that string database query failed. So now that I have this function I can just call confirmed query. Since I've loaded it in my functions here I'll have it available to me. Let's just call confirmed query on result.

I can take all of that out. To me, that's a little cleaner. Then I can just check, it's does a check to see did the query work or not, and then it moves on from there. And again, because I now have reusable code, if I want to make improvements to this. If I want to change the message that gets displayed or something else. I can just do it one place, and the way the confirm query gets handled will trickle down throughout my entire site. So let's just close all of that up, let's go back one more time to manage contact and make sure that the page still works, and it does. So there's one last thing that I want us to do before we leave database connectivity and that's just that i want us to open up the DB connection. And instead of having these variables that we defined here, a better way to do it is to use constants.

So I'm just going to copy and paste in an example of what I'm talking about. You can just define, all of these as constants instead. I'll get rid of those, and then instead of having it here, we'll DB server, DB user, DB Pass and DB Name. Now it's using constants for those instead of the variables. It's just a little bit better practice to do it this way since they are, in fact, going to be constant values. They're not going to vary, we would use constants for them. And let's save it and just one last time let's make sure we didn't break anything.

Go back over to Firefox and reload our page and you see this still comes up just fine.

Show transcript

This video is part of

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

131 video lessons · 34461 viewers

Kevin Skoglund
Author

 
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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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