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Working with retrieved data

From: PHP with MySQL Essential Training

Video: Working with retrieved data

We've learned how to connect to MySQL using PHP and how to access the results that it returns. In this movie we're going to look a little closer at some of the options we have for working with those results sets. There are four ways to retrieve data from the query result, and the first of these we've already seen, it's mysqli_fetch_row. And it brings back a row of data and assigns it to a standard array. The keys for each one of those columns are going to be integers. So if we want to get the menu name, we ask for what's in column one. That's the index position in the array one.

Working with retrieved data

We've learned how to connect to MySQL using PHP and how to access the results that it returns. In this movie we're going to look a little closer at some of the options we have for working with those results sets. There are four ways to retrieve data from the query result, and the first of these we've already seen, it's mysqli_fetch_row. And it brings back a row of data and assigns it to a standard array. The keys for each one of those columns are going to be integers. So if we want to get the menu name, we ask for what's in column one. That's the index position in the array one.

We have another option though. We can use mysqli_fetch_assoc in its place, use it exactly the same way. The only difference is that the results are going to be returned in an associative array. That's nice because now the keys are going to be the column names. If we want to get menu name for our subject, well then we ask for the key menu name. It's nice and easy, it is a touch slower, because it does have to make an extra query to MySQL to find out the column names. So it can use them when it's constructing that associative array.

But you won't notice a speed difference. Then we have a third option, which is mysqli_fetch_array. Again, used in exactly the same way, but this time, the results are returned in either a standard array, or an associative array, or both. Which is essentially an associative array that indexes it both by integers and by the column names. Now by default, it's going to do both, that's configurable. The last argument that you pass in can be a constant that will tell it either to return a number index, an associative array with the column index or both. By default it's going to do both, which is going to make your data set and your memory a lot larger.

So I think that the best one to use, the one that's easiest and most convenient is the ASSOC version. If you want it indexed by number, or if you want the one that's just absolutely as fast as possible, you'll want to use fetch row. Mysqli_fetch_array, you should really only use if you need the convenience of being able to switch back and forth between the integer version. And the column name version, and you don't mind the extra memory that it takes up and the extra speed. Now, when I say that it's slower, I mean, you won't really notice a difference until you're doing something like 100,000 queries per second.

Like, you really aren't going to notice the difference until you start doing a lot and lot of queries. But once you get to that point, it does make sense to optimize and pick the one that's fastest and still meets your needs. Now, I said there were 4, there's a fourth one, which is mysqli_fetch_object. And that's going to be when we're working with object oriented programming. We can have it fetch back the data and go ahead and populate an object with it. That's going to be even slower but its going to really depend on the size of your object as to how slow it is. We're not going to be using that one but let's take a look at the other three. So let's just open back up our databases.php file. And you can see we were doing mysqli_fetch_row first. Go back and just remind ourselves what that looks like, we'll hit Reload. You can see that all of these are indexed by an integer, 0, 1, 2, 3. Now let's try the other version, we simply change this to be assoc, Save it, come back and reload the page.

Look at that, now the index is id, menu name, position, and visible. Much easier to access it that way. And then last of all, let's just try array, there we go. We'll reload it, and you'll see that we actually get an associative array that has both. See, everything is repeated twice, so we have it both indexed by the number 1 and by menu name, so you can see why this takes up more memory. And also takes more time for it to construct. Now they said, you can use mysql_fetch_array and just pass in another argument here, MYSQL_ASSOC. And now we come back over here and reload it and it basically does the same thing as the assoc function does.

It has the same behavior. So you can do it one way or the other. I tend to just stick with assoc and that's what we're doing for the rest of the string. We'll be doing it that way so that we can refer to it by it's column name. Let's try that here, instead of just dumping each one out, let's actually modify this. Take this out, and let's echo back row, it's a associated array, so then we can just ask it for it's id. And then I'll just put a br tag at the end and then let's just Copy that line. I'm going to paste it, there we go, a few more times. And then, I can just change it so that I'm asking for each one of those keys. Menu name, position, and visible.

But let's just go back over here and reload our page, and there we go. Now we're seeing our actual values, we're not just doing a var dump anymore. We're accessing the values in the associative array that it returned, that it assigned to a row. It's just a regular PHP associative array at this point and we're accessing it by using these keys. Now this still is probably a little rough from what you would want from an actual use case. Let's try something a little different, let's put in ul tags here at the top and bottom, ul tags and for each one of these items here, let's stop our PHP for a second.

Let's put in an li tag, and then let's just grab this echo menu name and let's put that here inside php tags with a semicolon after it. We'll get rid of all of this except that we need to turn back on our php tags here. Okay, see how that works? I'm breaking my loop, I'm stopping doing php briefly here, this is a php block. Then I stop in the middle of the loop, do some html, switch back into php, and then I do need to switch back into php just to get that closing brace in for my loop. Now I'm going to have an unordered list that outputs. So let's try this.

Let's just go back real quick, reload the page, and there we go. That's the kind of thing that you'd potentially want to use on your website. And that's exactly what we're going to be doing a little later. The one last thing I want to mention is that I just called it row. It's just generic that it's a row and you can certainly use that, but I think it's even better to assign it something that's useful. So if you're working with a customer, you're using a customer table, well then call it customer. If you're bringing back orders, call it order. So in this case, we're working with subjects, so I'm going to say that this is a subject. So there we go, it's a little cleaner. So while I'm getting back a subject, the subject's menu name is what I want to display.

Think that makes it nice and easy, and it's a lot easier to read the code and understand what's going on than using something just generic like row. So now that we've seen how to read data from the database, let's look at the other parts of CRUD, creating, updating, and deleting.

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This video is part of

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

131 video lessons · 33243 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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