I have the code below code that works correctly as what i want. It does not send any output on browser that is what i exactly want.
ob_start();
echo "test";
echo "test";
$output = ob_get_clean( );
But problem is in my below code. below code start sending the output on the browser even i have $output = ob_get_clean( ); at the end
ob_start();
for($i=0;$i<=10000000;$i++){
echo $i."<br/>";
}
$output = ob_get_clean( );
I am unable to understand the concept of output buffering. everyone say you can control the output and send the output when you want but my above script start sending output to the browser.
There's a limit to how much there can be buffered which by default is 4KB so you are hitting the maximum with your script. If you want to use it for a larger buffer you have to edit your php.ini settings to reflect that. To quote from the PHP docs
You can enable output buffering for all files by setting this directive to ‘On’. If you wish to limit the size of the buffer to a certain size – you can use a maximum number of bytes instead of ‘On’, as a value for this directive (e.g., output_buffering=4096). As of PHP 4.3.5, this directive is always Off in PHP-CLI. source
The PHP doc is quite technical on the subject so I found this blog post which explains the bits and tricks to output buffering:
Streaming and Output Buffering
Related
I am absolutely stumped here. I must either be missing something very simple or dont understand how this works.
Output buffering does not work at all on MAMP PRO, all contents are simply being displayed on the page and nothing goes to the buffer, not even hello world. I have tried every example
I am creating a simple framework and output buffering just does not work.
I have a module class with a function that includes a file and the code simply shows on the page without me even clearing the buffer.
I have checked the php.ini file in both loaded configuration file and the configuration file shows output_buffering = 4096.
I am so confused
Here is the code example:
//index.php
var_dump(ob_start());//returns true
echo "Hello World"; //prints straight to the screen
include MODULES.'/home.php'; //output comes straight out
var_dump(ob_get_contents());//Shows html string
$test = ob_get_contents();
echo $test; //Output gets displayed twice
In PHP.ini:
output_buffering=4096;
ob_get_contents does not clear the buffer so when a script ends it is flushed to the output as usual.
If you only want to get data as string and clear buffer use ob_get_clean()
You can think of output buffering as creating "bookmarks" or "restore points" in output buffer. For example:
buffer is empty
echo 'hello' - output buffer has "hello" string
ob_start() - "bookmark" is created
echo 'world' - output buffer has two lines "hello" and "world" strings
ob_get_contents() - returns output buffer content since last "bookmark" - returns "world", but buffer contents stay the same
scripts ends and flushes whole output buffer to screen
if you use ob_get_clean() instead it returns contents since last "bookmark" and deletes it from output buffer - the buffer has only "hello" in it
EDIT: I know it's very simple and naive explanation but I recall it helped me a lot to grasp the concept.
i know those methods related to output buffering:
<?php
ob_start();
// some code
ob_end_flush();
ob_end_clean();
but i can't figure out why will i need the length of the output buffer. there is one question here is SOF about measuring the bandwidth of the user ,although that calculation will need to measure pictures and other files which is not addressed.
i did check the PHP manual and the "why" is not there.
Answering "why to use it". In order to answer this, we must first understand why we need to use ob_start.
Usually it is used for two purpose:
When we want to send HTTP headers, but we are not sure, that there is no rendering before(the first output will trigger header sending, so if you use, echo for example, before header, the later won't work)
When we want to send our output by chunks for performance. (your code can be written with a lot of echo or print, and usually they outputing only small data, so you are sending small portions of data back to browser, which is affecting performance.)
So now you can start to guess, why we need to use ob_get_length(). For example: i want to send my output by large chunks, so i am enabling output buffering and with the help of ob_get_lengthi can control how many data i can write to buffer, before sending it.
ob_get_length will return the length of the contents in the output buffer..
Here is simple example..
<?php
ob_start();
echo "Hello ";
$len1 = ob_get_length();
echo "World";
$len2 = ob_get_length();
ob_end_clean();
echo $len1 . ", ." . $len2;
?>
The above example will output: 6, 11
Updated:
ob_get_length() is helpful if you want to send a custom HTTP Content-Length header - although that is for advanced users only!
This is a sample code from the book I am reading:
ob_start();
include("{$path}.ini");
$string = ob_get_contents();
ob_end_clean();
$pairs = parse_ini_string($string);
My question is, how does ob_get_contents() know what to get contents from? ({$path}.ini in this situation)?
ob_get_contents simply gets the contents of the output buffer since you called ob_start(). Essentially, an output buffer in PHP catches anything that would have been output to the browser (excluding headers). It's useful in cases where you may need to filter some output, or you're using a PHP method (such as var_dump) that writes output directly to screen, and you would instead like the return value of the method in a string.
In this case, because you're include()ing the .ini file, it's contents will be essentially output to screen, and ob_get_contents() will get the content of the file.
If you were to put echo "I'm a little teapot short and stout"; underneath the include, this would also be included in $string after the body of the .ini file.
In your specific case, however, output buffering is an unnecessary overhead, simply use file_get_contents on the .ini file. I'm not sure why a book would even have this code in it at all.
The "ob" stands for "output buffer". When you call ob_start(), PHP reroutes all output (using echo, etc) to the output buffer. Then you can use the other ob_* functions to retrieve and/or clear the buffer contents.
In your example, it will buffer any output generated by the file referenced by "{$path}.ini". When you include it, its output is added to the buffer, and when you call ob_get_contents(), it retrieves the contents of the buffer.
From PHP:
ob_start — Turn on output buffering
ob_get_contents — Return the contents of the output buffer
ob_end_clean — Clean (erase) the output buffer and turn off output buffering
Now, ob_get_contents can collect all buffer that outputted.
[1] http://www.php.net/manual/en/book.outcontrol.php
ob_get_contents() is getting everything that is echoed after calling ob_start() function, so there is not anything special about {$path}.ini - you are required to echo data you want to collect (yes, even outputs of simple echo or print_r calls will be collected - sometimes useful for debugging simple scripts).
You may understand ob_start() function as a simple redirection from screen to (invisible) PHP internal buffer which is later read by ob_get_contents(). So you will be able to redirect anything that you may see on the screen without calling ob_start() function (even the whole web pages).
In my website(running with drupal) the ob_flush function takes a long time(between 10 - 100 secs) to be executed. How do I find out why? What can cause this so long time?
Try this:
ob_start();
//Your code to generate the output
$result = ob_get_contents(); //save the contents of output buffer to a string
ob_end_clean();
echo $result;
It is run quick for me.
[You may want to tag your question with Drupal, since this feels like it might be a Drupal issue. Specifically, I suspect that when you flush the buffer, you're writing to an outer buffer, which triggers a ton of hooks to be called to filter the data you've just written.]
I suspect that your problem is nested buffers. Drupal really likes buffers and buffers everything all over the place. Check the result of:
echo "<pre>\nBuffering level: ";
. ob_get_level() .
. "\nBuffer status:\n"
. var_dump(ob_get_status(TRUE))
. "\n</pre>";
If you've got nested buffers, then I suspect ob_flush() will do nothing for you: it just appends the contents of your inner buffer into the next outermost layer of buffering.
Nested buffers can come from Drupal itself (which the above will show), or from the settings for zlib-output-compression and output_buffering (try twiddling those, see if it changes anything).
If your buffers are not nested, and the above settings do not help, then you may also want to split the operation into pieces, and run the profiler there, to see which part is taking the time:
$data = ob_get_contents(); // Return the contents of the output buffer.
ob_clean(); // Clean (erase) the output buffer.
ob_end(); // Close the buffer.
echo($data); // Output our data - only works if there's no outer buffer!
ob_start(); // Start our buffer again.
The question then becomes, though, "what are you trying to accomplish?" What do you think ob_flush() is doing here? Because if the answer is "I want to push everything I've done so far to the browser"... then I'm afraid that ob_flush() just isn't the right way.
SET
output_buffering = Off
in php.ini
use
<?ob_start();?>
at the beginning of the page and
<?ob_flush();?>
at the end of the page, to solve this problem.
Firstly, I want to echo text and ,after 5 seconds,I want to echo another text.
So I write...
<?php
echo 'Text';
flush();
sleep(5);
flush();
echo 'Another Text';
?>
But I see both of (Text Another Text ) after 5 seconds.How can I do for this?
From documentation
Several servers, especially on Win32, will still buffer the output from your script until it terminates before transmitting the results to the browser.
So you see both TextAnother Texttogether.
Take a look at output buffering.
Have you started output buffering at some time? If so, you need to use ob_end_flush() to flush.
Switch off output buffering if you have it on or call ob_flush() too. Any output compressing (like gzip) will also mess it up. If it doesn't work try modifying these two php.ini directives to:
output_buffering = off
zlib.output_compression = off