Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Creating an instance of a specific class with a database result

From: Accessing Databases with Object-Oriented PHP

Video: Creating an instance of a specific class with a database result

We've seen how to set the properties of an Incidentally, you can find both of these files in So, we've got a prepared statement that is selecting So car is now our new object that has been created using our database query.

Creating an instance of a specific class with a database result

We've seen how to set the properties of an existing PHP object from the result of a select query. PDO can also create a new object and set its properties, but you need to be careful that default values in the object constructor don't overwrite the values from the database result. We'll use the same Car class as in the previous video. And the script in fetch_class.php is also very similar. The only difference is that we're not actually creating an object beforehand.

We're going to use the results of the database query to create our new object. Incidentally, you can find both of these files in the chapter four, 04_03 folder of the exercise files. So, we've got a prepared statement that is selecting values from the cars database and it's using car_id. That's got a question mark as the placeholder. We then prepare the statement and then we execute the statement, parsing at the value of car_id, which is bound to that placeholder. So, we can now use the database result to create an instance of the object that we want. First, we need to set the fetch mode on the statement. So let's add some new code here. We need the statement object and the setFetchMode method. The first argument that we need to pass is a PDO constant. This time, it's PDO, double colon, and its fetch class, FETCH_CLASS. The second argument is the name of the class definition as a string, so it's Car.

And the third argument is an array of any values that need to be passed as arguments to the class constructor. There's just one value we need to pass. That's the car ID, so we need an array with a single element in it, which is car_id. Then we can call the fetch method and assign the result to the object that we're creating from the select query. So we'll call our object car, statement fetch. So car is now our new object that has been created using our database query.

Because the class uses the magic toString method, we can inspect it using echo. We'll just car, and then if we save that, and load the page into a browser. We've created our object, but probably that's not the result that you were expecting. It's got the correct car ID, but it's got all of the default values instead of the values that have been drawn from the database. And the reason that's happened is that the PDO fetch class mode calls the constructor after populating the properties with the database result. Consequently, the default values overwrite the ones that we want to use. And that's part of the problem. It's using default values in the constructor. Let's go back to the editing program and see what happens if we comment out these default values here in the car constructor.

We just save that. Go back to the browser and refresh. We now get the values that have been drawn from that database query. Well, that works, but it's not very practical. You don't want to have to comment out default values in your class constructors. So let's go back and see how we can fix this. First, we'll uncomment those and save that, and then go back to fetch_class.php. What we need to do is combine this PDO FETCH_CLASS constant with another constant. So, put the cursor immediately before the comma, then type a vertical pipe. And the other one is PDO, and then two colons and its FETCH, then underscore PROPS_LATE.

There we are. And what this does is it calls the class constructor first and then uses the properties that have been drawn from the database to set various properties within the new object. So if we save that, go back to the browser. If we refresh, we should still have those values there. And we can just check it by going back and changing to a different ID. Let's choose 25. Save that. Refresh. And now we're getting the correct values that we want.

So to create an instance of an object from a database result, mapping the columns to properties of the same name in the class, you need to set the fetch mode to PDO FETCH_CLASS. The second argument is the class name. And the third argument is an array of arguments to pass to the class constructor. But used on its own, PDO FETCH_CLASS calls the constructor after setting the object's properties. So default properties overwrite those obtained from the database result. To call the constructor first, you need to combine PDO FETCH_CLASS and PDO FETCH_PROPS_LATE.

And you combine two constants like this by separating them with a vertical pipe. One final point, the class definition needs to use the magic set method to set the property values. It won't work with custom setter methods.

Show transcript

This video is part of

Image for Accessing Databases with Object-Oriented PHP
Accessing Databases with Object-Oriented PHP

47 video lessons · 3012 viewers

David Powers
Author

 
Expand all | Collapse all
  1. 13m 33s
    1. Welcome
      1m 4s
    2. What you should know before watching this course
      2m 8s
    3. Using the exercise files
      4m 56s
    4. Setting SQLite permissions
      1m 11s
    5. A quick primer on using PHP objects
      4m 14s
  2. 10m 12s
    1. Overview of PHP database APIs
      4m 5s
    2. Using prepared statements
      4m 24s
    3. Using transactions
      1m 43s
  3. 48m 57s
    1. Creating a database source name
      2m 3s
    2. Connecting to a database with PDO
      7m 27s
    3. Looping directly over a SELECT query
      3m 49s
    4. Fetching a result set
      8m 3s
    5. Finding the number of results from a SELECT query
      7m 14s
    6. Checking if a SELECT query contains results
      3m 32s
    7. Executing simple non-SELECT queries
      6m 2s
    8. Getting error messages
      7m 17s
    9. Using the quote() method to sanitize user input
      3m 30s
  4. 39m 51s
    1. Binding input and output values
      2m 36s
    2. Using named parameters
      9m 51s
    3. Using question marks as anonymous placeholders
      2m 35s
    4. Passing an array of values to the execute() method
      5m 20s
    5. Binding results to variables
      7m 53s
    6. Executing a transaction
      6m 54s
    7. Closing the cursor before running another query
      4m 42s
  5. 21m 20s
    1. Generating an array from a pair of columns
      2m 44s
    2. Setting an existing object's properties with a database result
      4m 42s
    3. Creating an instance of a specific class with a database result
      6m 1s
    4. Reusing a result set
      7m 53s
  6. 38m 14s
    1. Connecting to a database with MySQLi
      5m 57s
    2. Setting the character set
      1m 57s
    3. Submitting a SELECT query and getting the number of results
      4m 4s
    4. Fetching the result
      7m 35s
    5. Rewinding the result for reuse
      3m 20s
    6. Handling non-SELECT queries
      5m 27s
    7. Getting error messages
      5m 47s
    8. Sanitizing user input with real_escape_string()
      4m 7s
  7. 27m 49s
    1. Initializing and preparing a statement
      4m 17s
    2. Binding parameters and executing a prepared statement
      5m 55s
    3. Binding output variables
      5m 6s
    4. Executing a MySQLi transaction
      7m 5s
    5. Dealing with "commands out of sync" in prepared statements
      5m 26s
  8. 24m 7s
    1. Buffered and unbuffered queries
      4m 19s
    2. Using real_query()
      6m 1s
    3. Freeing resources that are no longer needed
      2m 31s
    4. Submitting multiple queries
      6m 41s
    5. Creating an instance of a class from a result set
      4m 35s
  9. 3m 31s
    1. PDO and MySQLi compared
      3m 31s

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ .

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed Accessing Databases with Object-Oriented PHP.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member ?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferences from the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Learn more, save more. Upgrade today!

Get our Annual Premium Membership at our best savings yet.

Upgrade to our Annual Premium Membership today and get even more value from your lynda.com subscription:

“In a way, I feel like you are rooting for me. Like you are really invested in my experience, and want me to get as much out of these courses as possible this is the best place to start on your journey to learning new material.”— Nadine H.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.