Output Buffering Control

Introduction

The Output Control functions allow you to control when output is sent from the script. This can be useful in several different situations, especially if you need to send headers to the browser after your script has begun outputting data. The Output Control functions do not affect headers sent using header() or setcookie(), only functions such as echo and data between blocks of PHP code.

Installing/Configuring
- Runtime Configuration
Predefined Constants
Output Buffering
Flushing System Buffers
User-Level Output Buffers
Examples
- Basic usage
- Output rewrite usage
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 1 note

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clancy hood at gmail dot com ¶

16 years ago

The manual is a little shy on explaining that output buffers are nested, and that "turns off output buffering" means turning off the highest nested buffer.  See ob_get_level (for a useful function, but still no explanation)

<?php
    ob_start();
    echo "1:blah\n";
    ob_start();
    echo "2:blah";
    // ob_get_clean() returns the contents of the last buffer opened.  The first "blah" and the output of var_dump are flushed from the top buffer on exit
    var_dump(ob_get_clean());
    exit;
?>

puts:
    1:blah
    string(6) "2:blah"

Prior to realising this, I had thought PHP's ob functionality left more to be desired.  I *really* wish I knew earlier.

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