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(). To output what is stored in the internal buffer, use ob_end_flush(). Alternatively, ob_end_clean() will silently discard the buffer contents.
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($_SERVER['SCRIPT_FILENAME'])) in the
Output buffers are stackable, that is, you may call ob_start() while another ob_start() is active. Just make sure that you call ob_end_flush() the appropriate number of times. If multiple output callback functions are active, output is being filtered sequentially through each of them in nesting order.
An optional output_callback function may be
specified. This function takes a string as a parameter and should
return a string. The function will be called when
ob_end_flush() is called, or when the output buffer
is flushed to the browser at the end of the request. When
output_callback is called, it will receive the
contents of the output buffer as its parameter and is expected to
return a new output buffer as a result, which will be sent to the
browser. If the output_callback is not a
callable function, this function will return
If the callback function has two parameters, the second parameter is
filled with a bit-field consisting of
If output_callback returns
input is sent to the browser.
The output_callback parameter may be bypassed
by passing a
ob_clean(), ob_flush() and
ob_start() may not be called from a callback
function. If you call them from callback function, the behavior is
undefined. If you would like to delete the contents of a buffer,
return "" (a null string) from callback function.
You can't even call functions using the output buffering functions like
print_r($expression, true) or
highlight_file($filename, true) from a callback
If the optional parameter chunk_size is passed, the callback function is called on every first newline after chunk_size bytes of output. Default value 0 means that the function is called only in the end, other special value 1 sets chunk_size to 4096.
If the optional parameter erase is set to
the buffer will not be deleted until the script finishes (as of PHP 4.3.0).
This function was changed to return |
// replace all the apples with oranges
return (str_replace("apples", "oranges", $buffer));
<p>It's like comparing apples to oranges.</p>
The above example will output:
<p>It's like comparing oranges to oranges.</p>