Shulou(Shulou.com)06/02 Report--

This article mainly introduces "how php shuts down ob_start". In daily operation, I believe many people have doubts about how php closes ob_start. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts about "how php shuts down ob_start". Next, please follow the editor to study!

Php ob_start is used to turn on the output control buffer, and when ob_start is turned off, the contents of the buffer can be silently discarded using the ob_end_clean () function.

This article operating environment: windows7 system, PHP7.1 version, DELL G3 computer

How does php shut down ob_start?

Ob_start-turn on output control buffering

Description

Ob_start (callable $output_callback = null, int $chunk_size = 0, int $flags = PHP_OUTPUT_HANDLER_STDFLAGS): bool

This function turns on output buffering. When output buffering is activated, the script will not output the content (except for the http header). Instead, the content that needs to be output is stored in the internal buffer.

The contents of the internal buffer can be copied into a string variable using the ob_get_contents () function. To output what is stored in the internal buffer, you can use the ob_end_flush () function. In addition, using the ob_end_clean () function silently discards the contents of the buffer.

Warning

When there is a callback function being called, some network servers (such as Apache) change the working directory of a script. You can change it back in the callback function, such as chdir (dirname ($_ SERVER ['SCRIPT_FILENAME'])).

The output buffer is stackable, which means that when one ob_start () is active, you can call another ob_start (). Just make sure that ob_end_flush () is called correctly the appropriate number of times. If multiple output callback functions are active, the output will always be filtered through them in nested order.

Parameters.

Output_callback

The optional parameter output_callback function can be specified. This function takes a string as an argument and returns a string. This function is called when the output buffer is flushed (sent) or cleaned by (ob_flush (), ob_clean (), or similar function), or when the contents of the output buffer are flushed to the browser at the end of the request. When output_callback is called, it takes the contents of the output buffer as a parameter and expects to return a new output buffer as a result, and the contents of the new output buffer are sent to the browser. If the output_callback is not a callable function, the function returns false.

The following is the callback signature:

Handler (string $buffer, int $phase =?): string

Buffer

Output the contents of the buffer.

Phase

Bitmask PHP_OUTPUT_HANDLER_* constant.

If output_callback returns false, its original input is sent directly to the browser.

This parameter output_callback can be avoided by directly giving a null value.

Ob_end_clean (), ob_end_flush (), ob_clean (), ob_flush (), and ob_start () cannot be called from a callback function. If they are called from the callback function, the resulting behavior is ambiguous. If you want to delete the contents of the buffer, return a "(empty string) from the callback function. You can't use output buffering functions like print_r ($expression, true) or highlight_file ($filename, true) from a callback function.

Note: ob_gzhandler () function exists to facilitate sending gz-encoded data to web browsers that support compressed web pages. Ob_gzhandler () determines what type of content encoding the browser will accept and will return its output accordingly.

Chunk_size

If the optional parameter chunk_size is assigned, the buffer will be flushed after any output operation that causes the length of the buffer to equal or exceed chunk_size. The default value of 0 means that the function is called only at the end.

Prior to PHP 5.4.0, 1 was a special case value, which meant that the chunk_size was set to 4096 bytes.

Flags

The flags parameter represents a mask bit that is used to control the operation on the buffer. The default is to allow output buffers to be cleaned, flushed and removed, which can be set explicitly via PHP_OUTPUT_HANDLER_CLEANABLE | PHP_OUTPUT_HANDLER_FLUSHABLE | PHP_OUTPUT_HANDLER_REMOVABLE, or PHP_OUTPUT_HANDLER_STDFLAGS as shorthand.

Return value

Returns true on success or false on failure.

At this point, the study on "how php shuts down ob_start" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.