OB_START(3)								 1							       OB_START(3)

ob_start - Turn on output buffering

SYNOPSIS

       bool ob_start NULL PHP_OUTPUT_HANDLER_STDFLAGS ([callable  $output_callback], [int  $chunk_size], [int  $flags])

DESCRIPTION

	This  function	will  turn  output  buffering on. While output buffering is active no output is sent from the script (other than headers),
       instead the output is stored in an internal buffer.

	The contents of this internal buffer may be copied into a string variable using ob_get_contents(3). To output what is stored in the inter-
       nal buffer, use ob_end_flush(3). Alternatively, ob_end_clean(3) will silently discard the buffer contents.

       Warning

	       Some  web servers (e.g. Apache) change the working directory of a script when calling the callback function. You can change it back
	      by e.g.  chdir(dirname($_SERVER['SCRIPT_FILENAME'])) in the callback function.

	Output buffers are stackable, that is, you may call ob_start(3) while another  ob_start(3)  is	active.  Just  make  sure  that  you  call
       ob_end_flush(3)	the  appropriate  number of times. If multiple output callback functions are active, output is being filtered sequentially
       through each of them in nesting order.

PARAMETERS

	      o $output_callback
		- An optional $output_callback function may be specified. This function takes a string as a parameter and should return a  string.
		The  function  will  be called when the output buffer is flushed (sent) or cleaned (with ob_flush(3), ob_clean(3) or similar func-
		tion) or when the output buffer is flushed to the browser at the end of the request. When  $output_callback  is  called,  it  will
		receive  the  contents of the output buffer as its parameter and is expected to return a new output buffer as a result, which will
		be sent to the browser. If the $output_callback is not a callable function, this function will return FALSE. This is the  callback
		signature:
		string handler (string	$buffer, [int  $phase])

		     o $buffer
		       - Contents of the output buffer.

		     o $phase
		       - Bitmask of PHP_OUTPUT_HANDLER_* constants.

	       If $output_callback returns FALSE original input is sent to the browser.  The $output_callback parameter may be bypassed by passing
	      a NULL value. ob_end_clean(3), ob_end_flush(3), ob_clean(3), ob_flush(3) and ob_start(3) may not be called from a callback function.
	      If  you call them from callback function, the behavior is undefined. If you would like to delete the contents of a buffer, return ""
	      (a null string) from callback function. You can't even call functions using the output buffering functions like print_r($expression,
	      true) or highlight_file($filename, true) from a callback function.

	      Note

		      In  PHP  4.0.4, ob_gzhandler(3) was introduced to facilitate sending gz-encoded data to web browsers that support compressed
		     web pages. ob_gzhandler(3) determines what type of content encoding the browser  will  accept  and  will  return  its  output
		     accordingly.

	      o $chunk_size
		-  If  the  optional  parameter  $chunk_size is passed, the buffer will be flushed after any output call which causes the buffer's
		length to equal or exceed $chunk_size. The default value 0 means that the output function will only be called when the output buf-
		fer is closed.	Prior to PHP 5.4.0, the value 1 was a special case value that set the chunk size to 4096 bytes.

	      o $flags
		-  The	$flags	parameter  is a bitmask that controls the operations that can be performed on the output 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_OUT-
		PUT_HANDLER_FLUSHABLE | PHP_OUTPUT_HANDLER_REMOVABLE, or PHP_OUTPUT_HANDLER_STDFLAGS as shorthand.  Each flag controls access to a
		set of functions, as described below:

	      +-----------------------------+---------------------------------------------------+
	      | 	 Constant	    |							|
	      | 			    |							|
	      | 			    |			  Functions			|
	      | 			    |							|
	      +-----------------------------+---------------------------------------------------+
	      | 			    |							|
	      |PHP_OUTPUT_HANDLER_CLEANABLE |							|
	      | 			    |							|
	      | 			    | ob_clean(3),	   ob_end_clean(3),	    and |
	      | 			    | ob_get_clean(3).					|
	      | 			    |							|
	      | 			    |							|
	      |PHP_OUTPUT_HANDLER_FLUSHABLE |							|
	      | 			    |							|
	      | 			    | ob_end_flush(3),	       ob_flush(3),	    and |
	      | 			    | ob_get_flush(3).					|
	      | 			    |							|
	      | 			    |							|
	      |PHP_OUTPUT_HANDLER_REMOVABLE |							|
	      | 			    |							|
	      | 			    | ob_end_clean(3),	     ob_end_flush(3),	    and |
	      | 			    | ob_get_flush(3).					|
	      | 			    |							|
	      +-----------------------------+---------------------------------------------------+
RETURN VALUES

	Returns TRUE on success or FALSE on failure.

CHANGELOG

       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 7.0.0	|						    |
       |	|						    |
       |	|  In  case  ob_start(3)  is  used inside an output |
       |	| buffer callback, this  function  will  no  longer |
       |	| issue   an  E_ERROR  but  instead  an  E_RECOVER- |
       |	| ABLE_ERROR, allowing	custom	error  handlers  to |
       |	| catch such errors.				    |
       |	|						    |
       | 5.4.0	|						    |
       |	|						    |
       |	|  The	third parameter of ob_start(3) changed from |
       |	| a boolean parameter called $erase (which, if	set |
       |	| to  FALSE,  would  prevent the output buffer from |
       |	| being deleted until the script  finished  execut- |
       |	| ing)	to  an	integer  parameter  called  $flags. |
       |	| Unfortunately, this results in an API compatibil- |
       |	| ity  break  for  code  written prior to PHP 5.4.0 |
       |	| that uses the  third	parameter.  See  the  flags |
       |	| example for an example of how to handle this with |
       |	| code that needs to be compatible with both.	    |
       |	|						    |
       | 5.4.0	|						    |
       |	|						    |
       |	|  A chunk size of 1 now results  in  chunks  of  1 |
       |	| byte being sent to the output buffer. 	    |
       |	|						    |
       | 4.3.2	|						    |
       |	|						    |
       |	|  This  function  was	changed  to return FALSE in |
       |	| case the passed $output_callback can not be  exe- |
       |	| cuted.					    |
       |	|						    |
       +--------+---------------------------------------------------+
EXAMPLES

       Example #1

	      User defined callback function example

	      <?php

	      function callback($buffer)
	      {
		// replace all the apples with oranges
		return (str_replace("apples", "oranges", $buffer));
	      }

	      ob_start("callback");

	      ?>
	      <html>
	      <body>
	      <p>It's like comparing apples to oranges.</p>
	      </body>
	      </html>
	      <?php

	      ob_end_flush();

	      ?>

	      The above example will output:

	      <html>
	      <body>
	      <p>It's like comparing oranges to oranges.</p>
	      </body>
	      </html>

       Example #2

	      Creating an uneraseable output buffer in a way compatible with both PHP 5.3 and 5.4

	      <?php

	      if (version_compare(PHP_VERSION, '5.4.0', '>=')) {
		ob_start(null, 0, PHP_OUTPUT_HANDLER_STDFLAGS ^
		  PHP_OUTPUT_HANDLER_REMOVABLE);
	      } else {
		ob_start(null, 0, false);
	      }

	      ?>

SEE ALSO

       ob_get_contents(3),  ob_end_clean(3),  ob_end_flush(3),	ob_implicit_flush(3),  ob_gzhandler(3), ob_iconv_handler(3), mb_output_handler(3),
       ob_tidyhandler(3).

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