&reftitle.runtime; &extension.runtime;

# Output Control configuration options

&Name; | &Default; | &Changeable; | &Changelog;
output_buffering | "0" | PHP_INI_PERDIR |
output_handler | NULL | PHP_INI_PERDIR |
implicit_flush | "0" | PHP_INI_ALL |
url_rewriter.tags | "a=href,area=href,frame=src,form=,fieldset=" | PHP_INI_ALL | Before PHP 7.1.0, this was used to set session's trans sid rewrite. From PHP 7.1.0, it is only used by `output_add_rewrite_var`.
url_rewriter.hosts | `$_SERVER['HTTP_HOST']` is used as default. | PHP_INI_ALL | Available as of PHP 7.1.0

&ini.php.constants; &ini.descriptions.title;

`output_buffering` `bool`/`int`

- 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). This directive is always Off in PHP-CLI.

`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.

  You cannot use both `mb_output_handler` with `ob_iconv_handler` and you cannot use both `ob_gzhandler` and zlib.output_compression.

  Only built-in functions can be used with this directive. For user defined functions, use `ob_start`.

`implicit_flush` `bool`

- &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`.

`url_rewriter.tags` `string`

- `url_rewriter.tags` specifies which HTML tags are rewritten by `output_add_rewrite_var` values. Defaults to `a=href,area=href,frame=src,input=src,form=`

  `form` is special tag. `<input hidden="session_id" name="session_name">` is added as form variable.

  Before PHP 7.1.0, url_rewriter.tags was used to specify session.trans_sid_tags. As of PHP 7.1.0, `fieldset` is no longer considered as special tag.

`url_rewriter.hosts` `string`

- `url_rewriter.hosts` specifies which hosts are rewritten to include `output_add_rewrite_var` values. Defaults to `$_SERVER['HTTP_HOST']`. Multiple hosts can be specified by ",", no space is allowed between hosts. e.g. `php.net,wiki.php.net,bugs.php.net`