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LXXIV. Output Control Functions

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 began 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.

Requirements

No external libraries are needed to build this extension.

Installation

There is no installation needed to use these functions; they are part of the PHP core.

Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

Table 1. Output Control configuration options

NameDefaultChangeable
output_buffering"0"PHP_INI_PERDIR|PHP_INI_SYSTEM
output_handlerNULLPHP_INI_PERDIR|PHP_INI_SYSTEM
implicit_flush "0"PHP_INI_PERDIR|PHP_INI_SYSTEM
For further details and definition of the PHP_INI_* constants see ini_set().

Here is a short explanation of the configuration directives.

output_buffering boolean/integer

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).

output_handler string

You can redirect all of the output of your scripts to a function. For example, if you set output_handler to mb_output_handler(), character encoding will be transparently converted to the specified encoding. Setting any output handler automatically turns on output buffering.

Note: You cannot use both mb_output_handler() with ob_inconv_handler() and you cannot use both ob_gzhandler() and zlib.output_compression.

Resource Types

This extension has no resource types defined.

Predefined Constants

This extension has no constants defined.

Examples

Example 1. Output Control example

<?php

ob_start();
echo "Hello\n";

setcookie ("cookiename", "cookiedata");

ob_end_flush();

?>

In the above example, the output from echo() would be stored in the output buffer until ob_end_flush() was called. In the mean time, the call to setcookie() successfully stored a cookie without causing an error. (You can not normally send headers to the browser after data has already been sent.)

See Also

See also header(), setcookie() and .

Table of Contents
flush -- Flush the output buffer
ob_clean --  Clean (erase) the output buffer
ob_end_clean --  Clean (erase) the output buffer and turn off output buffering
ob_end_flush --  Flush (send) the output buffer and turn off output buffering
ob_flush --  Flush (send) the output buffer
ob_get_contents --  Return the contents of the output buffer
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_gzhandler --  ob_start callback function to gzip output buffer
ob_implicit_flush --  Turn implicit flush on/off
ob_start -- Turn on output buffering
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