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Unsetting cookie values

From: PHP with MySQL Essential Training

Video: Unsetting cookie values

Now that we know how to set cookies, we know how to read back their values, we should talk about how we unset cookies. How do you get rid of them when you're done? A classic case of this could be when someone logs in you want to record their user ID but then when they log out you want to get rid of it. You want make them not logged in anymore. Well to do that we need to know how to unset them. Let me first show you the wrong way to do it. You do not want to do it by using the unset function. That's what we use on variables when we want to unset them, it'll unset their value. But think about it for a second, why would you not want to use unset on the cookie global parameter? Why would that not work? The reason why is because those are the values that came in from the last request.

Unsetting cookie values

Now that we know how to set cookies, we know how to read back their values, we should talk about how we unset cookies. How do you get rid of them when you're done? A classic case of this could be when someone logs in you want to record their user ID but then when they log out you want to get rid of it. You want make them not logged in anymore. Well to do that we need to know how to unset them. Let me first show you the wrong way to do it. You do not want to do it by using the unset function. That's what we use on variables when we want to unset them, it'll unset their value. But think about it for a second, why would you not want to use unset on the cookie global parameter? Why would that not work? The reason why is because those are the values that came in from the last request.

Says nothing about what the user has on their browser. This is just a result of what came in on the last request. Unless we provide the user with something different, that's what's going to keep coming in for every future request. Unsending it isn't going to change it, it's still going to be sent from the user's browser. We have to tell the user's browser hey browser, you have to change something on your end. And so to do that, we have to do it one of the right ways, which is by using the set cookie function. Set cookie with no value after it will set it to nothing.

It will empty it out. Now I personally don't like this way. To me this looks too much like it's a mistake and it's not clear what your intent really was. I think that it's better to be explicit about it and to say that the value is null. So set cookie with whatever name to the value null. And that will set it equal to nothing. Another very common way to do it is to set the expiration date to a date in the past. So that will tell the browser, hey browser this cookie's no good anymore. You need to chuck it, get rid of it. Now my preferred method is to combine the second and third ones. Just do both.

Tell it to set the cookie to null so that the value is gone. And tell it by the way that cookie's no good anymore, you can throw it away. And then the cookie should just disappear. Both of them should work on their own independently. We can do both together and make it super clear that that's what we're trying to do. Let's try it and see. So here I am on my cookies.php page again. And let's just bring up our browser so that we see that we've already got hello there. Reload the page. Hello is the value that I last had there. Make sure that you have a cookie set for this. So now let's try a couple of these different approaches.

So let's comment out this line so we can use it in the future. Let's just do set cookie name. And then let's reload the page. So here we go reload the page one time. It's still there. We talked about this in the last movie, remember? It's because what we're seeing here is sort the, the echo of it. The fact that it was sent in the last request. We still at the end of our response. We sent back the fact that this ought to be erased. So we need to reload the page a second time, and we'll see that it's actually gone because when the request came back to us after that response, the next request did not include in the cookie.

So therefore, this was empty. Make sure you're clear on that. So that worked, let's try setting it again. That's one way to do it. I'll just uncomment that line, save it, reload the page. Now I don't see it here. But it did set it. And you can check if you want, or you can just reload it again to make sure that we're comfortable with that fact. And then let's try the next one. We're going to take it down here. But this time, instead of the value, we're going to set it equal to null. We'll save it. Reload the page. Again we have to reload it a second time and you'll see that it's gone.

And then comment it out. We'll set the cookie back again and reload the page twice. There it is, hello. And now we're going to get rid of it again using this other method. This time though we're going to say the same thing. We'll put the value again for this first one and expire we're going to change to be time minus and it can be any time in the past. 3600 will be an hour ago or you can go ahead and set it to something more like a week ago or two weeks ago. Let's save it. Let's go back and reload the page twice. And sure enough it disappears that way too.

And like I said, the way that I prefer is to do it this way. Let's set it first before we do this. But the one we're going to do is both together. We'll put Kevin's recommendation for unsetting. There we go. We'll set it one more time, there it is and then comment that out. Let's try unsetting it and there it is. Let's go back and just assure ourselves. If we go to preferences, we look at cookies. Show cookies. And look for the cookie that is for a local host. I don't have any so you'll see that it's gone.

It's not there. But you can search for it to find it or scan down the list. So that's it, that's all there is to unsetting a cookie. Just make sure that you don't try and unset the values that are here because at that point, you're too late to unset it. You're not making any tangible effect on the user's browser, you're just changing what's happening in PHP only. and that's not going to actually accomplish it for you.

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This video is part of

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

131 video lessons · 32808 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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