LXXXI. Output Control Functions

介紹

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.

需求

建立這個延伸不需要任何外部程式庫。

安裝

這些函數是PHP核心的一部分,不需要安裝就可使用。

執行時期組態

php.ini中的設定會影響這些函數的行為。

表格 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().

這裡為簡短的結構指令說明。

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.

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

implicit_flush boolean

FALSE by default. Changing this to TRUE tells PHP to tell the output layer to flush itself automatically after every output block. This is equivalent to calling the PHP function flush() after each and every call to print() or echo() and each and every HTML block.

When using PHP within an web environment, turning this option on has serious performance implications and is generally recommended for debugging purposes only. This value defaults to TRUE when operating under the CLI SAPI.

See also ob_implicit_flush().

資源類型

這個延伸沒有定義任何資源。

預先定義常數

這個延伸沒有定義任何常數。

範例

範例 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.)

注: When upgrading from PHP 4.1 (and 4.2) to 4.3 that due to a bug in earlier versions you must ensure that implict_flush is OFF in your php.ini, otherwise any output with ob_start() will not be hidden from output.

參考

See also header() and setcookie().

內容目錄
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_clean --  Get current buffer contents and delete current output buffer
ob_get_contents --  Return the contents of the output buffer
ob_get_flush --  Flush the output buffer, return it as a string and turn off output buffering
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_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