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Output buffering

From: PHP with MySQL Essential Training

Video: Output buffering

In the last two movies we talked about headers and redirection. And one of the very important points about working with headers and redirection is that they have to come before any output to the HTML. And I stressed that several times. Unless there's one big caveat, which is that we can have output buffering turned on. And that's what we're going to talk about in this movie is what output buffering is. And how it works. Let me give you a metaphor to illustrate. Let's imagine, for a moment that our PHP code is a faucet and our web server is a glass.

Output buffering

In the last two movies we talked about headers and redirection. And one of the very important points about working with headers and redirection is that they have to come before any output to the HTML. And I stressed that several times. Unless there's one big caveat, which is that we can have output buffering turned on. And that's what we're going to talk about in this movie is what output buffering is. And how it works. Let me give you a metaphor to illustrate. Let's imagine, for a moment that our PHP code is a faucet and our web server is a glass.

And we're going to fill up that glass with the output of the HTML. So as we execute our PHP, code the output line by line is being sent to the web server. The web server as soon as it gets the first little drop of water has the headers established for what it's going to send. That's why we can't change them after we start sending that code or the water to it. And then once the page has completely finished rendering, then the web server will take that information that it has gathered up and send it all off to the browser.

So it accumulates in the web server. The web server starts the headers for it, accumulates all the data behind it and when it's done, ships it out the door. Now let's imagine that instead we have our PHP code of the web server but we have PHP's output buffer that's like a measuring cup. And instead of filling the glass directly we're going to fill up the measuring cup first. So that's what fills up with all our data and then when it's full or when we get to a certain point, a certain measure. We're going to take and then send it over to our web server. And fill up our web server with it and send it off. That's how output buffering works.

While it's still there in that measuring cup, it's still inside php, we still have access to it. That's why we're able to modify the headers. We haven't given anything over to the web server yet. We have it still in our buffer, change the headers in the buffer then it'll go to the web server at the end and at that point the headers have all been established by our PHP code. That's what output buffering is. Now we do pay a small performance penalty by turning on output buffering because we do take the time to do this extra step. We take a little bit of time to tell PHP put things together before you send them out the door instead of just expressing them right on to the web server. But I think that you'll find in most cases the performance penalty is not that high and the benefits to gain by having output buffering are pretty significant. There are two ways we can turn on this output buffer. The first is that we can open up our php.ini file and make the adjustment there.

The second is that we can do it on a page by page basis. So first let's open up our php.ini file. You'll remember that early on in the configuration chapter we set up in our sandbox something called my_phpinfo.php. And that should bring up all of your php info. And if we search that page for B,U,F,F,E,R. You'll see output buffering. Output buffering for me has no value. That means that it is turned off, it is not doing output buffering. If it had a size there, then that would be the size of our measuring cup.

That's how much it's going to buffer before it sends it. So let's remind ourselves where our php.ini file lives. If we go up to the top, you'll see that it tells us the loaded configuration file is right here at this path. So that's where it's located. Let's open up our command line and I'm just going to do nano on that file, php.ini. That's going to open it up in the Nano Text Editor and let's go ahead and do a find for output buffering. Ctrl+W allow me to search inside of there and I'm going to just look for buffer, output buffering, so it shows you the default value is off, development value 4096.

That's a pretty good and standard value, that 4096. But this is just code comments. This is not the actual setting of it. Let's just do another search in here, Ctrl+W, search for buffer again. All right, here's a paragraph all about output buffering. It explains how it works. It's everything that I just told you and a little bit more. And it goes on to then tell you that the possible values are On Off, or an integer. So right now we scroll down a little bit more, you'll see that mine is turned off. We did that back in the configuration. We made sure that it was turned off for this reason. Now I'm going to turn it back on.

Now I could simply type on but instead of having an unlimited output buffer, I'm going to go ahead and give it a limit. That's the idea of the measuring cup here that it will fill up at some point. It will take 4,000 characters before it fills up. So I have 4,000 characters in which to still change my headers before the output buffer is full and it sends it to the web server for the first batch. So now that I have that change. I can exit using Ctrl+X. And let's type a y for save the changes. And a Return to save them in place. Now you'll need to restart your web server.

Sudo apachectl restart. Wants my password. And there it is that's my password used to install software. Now it has restarted and my output buffering should be turned on. If we come back over here, we reload this page and once again search for buffer. I'll put buffering as now 4096, now output buffering is turned on. That means now that if you went back to the previous two movies again with modifying headers and page redirection you would be able to send white space before you do those redirects and header modifications.

Now addition to turning in on all the time for all the pages in the php and I can also turn it on on a page by page basis. And I do that by using a PHP function called ob_start for output buffer start and then when I'm done output buffer end flush. So that's going to start the buffer. Everything that happens after that will go in the buffer. And at the end I have to say okay, I'm done now. You're free to flush this over to the web server.

So your page starts with ob_start and ends with ob_end_flush. Very important though, ob_start has to come before any content. Just the same as the headers, otherwise we won't have started the output buffer. Will output a little bit of HTML. The headers are already sent, then we turn on the buffer but it's too late. So it has to be the very first thing that we do. Also it won't hurt to turn it on again if you've already turned it on in the php.ini file. So which one should you use? Should you set your php.ini file or should you set it in your application? I would say that it's better to set it in the php.ini file so you don't forget to do this for any page.

So if you just have it set there then it will always be on. However you need to understand that it means that if you put it on a server where it is not enabled it's not going to work. You're going to have to make sure the php.ini file has output buffering turned on and by default it usually is now so that shouldn't be a problem. If you're in doubt, if you're creating something that is going to go out to other servers out there and you're not in control of those php.ini files, then I would say use the page by page version and just make sure that you do it application-wide.

Maybe it's something that you always include in your template so that it always starts and ends the output buffering before you do anything else. And that way you'll get the maximum amount of compatibility. But for yourself, I think you can just turn it on your php ini file and be just fine.

Show transcript

This video is part of

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

131 video lessons · 39147 viewers

Kevin Skoglund
Author

 
Expand all | Collapse all
  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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