Output Control Functions

flush — Flush system output buffer
ob_clean — Clean (erase) the contents of the active output buffer
ob_end_clean — Clean (erase) the contents of the active output buffer and turn it off
ob_end_flush — Flush (send) the return value of the active output handler and turn the active output buffer off
ob_flush — Flush (send) the return value of the active output handler
ob_get_clean — Get the contents of the active output buffer and turn it off
ob_get_contents — Return the contents of the output buffer
ob_get_flush — Flush (send) the return value of the active output handler, return the contents of the active output buffer and turn it off
ob_get_length — Return the length of the output buffer
ob_get_level — Return the nesting level of the output buffering mechanism
ob_get_status — Get status of output buffers
ob_implicit_flush — Turn implicit flush on/off
ob_list_handlers — List all output handlers in use
ob_start — Turn on output buffering
output_add_rewrite_var — Add URL rewriter values
output_reset_rewrite_vars — Reset URL rewriter values

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User Contributed Notes 8 notes

down

17 years ago

It seems that while using output buffering, an included file which calls die() before the output buffer is closed is flushed rather than cleaned. That is, ob_end_flush() is called by default.

<?php
// a.php (this file should never display anything)
ob_start();
include('b.php');
ob_end_clean();
?>

<?php
// b.php
print "b";
die();
?>

This ends up printing "b" rather than nothing as ob_end_flush() is called instead of ob_end_clean(). That is, die() flushes the buffer rather than cleans it. This took me a while to determine what was causing the flush, so I thought I'd share.

down

Anonymous ¶

15 years ago

You possibly also want to end your benchmark after the output is flushed.

<?php
your_benchmark_start_function();

ob_start ();
for ($i = 0; $i < 5000; $i++)
    echo str_repeat ("your string blablabla bla bla", (rand() % 4) + 1)."<br>\n";

                              <----------
echo your_benchmark_end_function();      |
ob_end_flush (); ------------------------
?>

down

gruik at libertysurf dot fr ¶

20 years ago

For those who are looking for optimization, try using buffered output.

I noticed that an output function call (i.e echo()) is somehow time expensive. When using buffered output, only one output function call is made and it seems to be much faster.
Try this :

<?php
your_benchmark_start_function();

for ($i = 0; $i < 5000; $i++)
    echo str_repeat ("your string blablabla bla bla", (rand() % 4) + 1)."<br>\n";

echo your_benchmark_end_function();
?>

And then :

<?php
your_benchmark_start_function();

ob_start ();
for ($i = 0; $i < 5000; $i++)
    echo str_repeat ("your string blablabla bla bla", (rand() % 4) + 1)."<br>\n";

echo your_benchmark_end_function();
ob_end_flush ();
?>

down

-1

Attila Houtkooper ¶

9 years ago

Take care to take exceptions in the code in mind when using ob_start and ob_get_contents. If you do not do this, the number of calls to ob_start will not match those to ob_end and you're not gonna have a good time.

<?php
public function requireIntoVariable($path) {
    ob_start();

    try {
        require $path;
    } catch (Exception $e) {
        ob_end_clean();
        throw $e;
    }

    $output = ob_get_contents();
    ob_end_clean();
    return $output;
}
?>

down

-2

basicartsstudios at hotmail dot com ¶

17 years ago

Sometimes you might not want to include a php-file under the specifications defined in the functions include() or require(), but you might want to have in return the string that the script in the file "echoes".

Include() and require() both directly put out the evaluated code.

For avoiding this, try output-buffering:
<?php
ob_start();
eval(file_get_contents($file));
$result = ob_get_contents();
ob_end_clean();
?>
or
<?php
ob_start();
include($file);
$result = ob_get_contents();
ob_end_clean();
?>
which i consider the same, correct me if I'm wrong.

Best regards, BasicArtsStudios

down

-3

kend52 at verizon dot net ¶

19 years ago

I ran out of memory, while output buffering and drawing text on imported images. Only the top portion of the 5MP image was displayed by the browser.  Try increasing the memory limit in either the php.ini file( memory_limit = 16M; ) or in the .htaccess file( php_value memory_limit "16M" ). Also see function memory_get_usage() .

down

-2

kamermans at teratechnologies dot net ¶

18 years ago

Output buffering is set to '4096' instead of 'Off' or '0' by default in the php-5.0.4-10.5 RPM for Fedora Core release 4 (Stentz).  This has cost me much time!

down

-5

della at sun dot com ¶

15 years ago

Sometimes users are blaming about slow pages ... not being aware that mostly this is due to network issues.

So I've decided to add some statistics at the end of my pages:



At beginning I start the counters:



<?php

  function microtime_float() { 

    if (version_compare(PHP_VERSION, '5.0.0', '>'))  return microtime(true);

    list($u,$s)=explode(' ',microtime()); return ((float)$u+(float)$s);  

  }

  $initime=microtime_float();

  ob_start();

  ob_implicit_flush();

?>



And at the end I show the statistics:



<?php

  echo "PHP Time: ".round((microtime_float()-$initime)*1000)." msecs. ";

  echo "Size: ".round_byte(strlen(ob_get_contents()));

  ob_end_flush();

?>



(round_byte is my function to print byte sizes)

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Output Control Functions

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User Contributed Notes 8 notes