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ob_start

ob_start

Turn on output buffering

bool **ob_start**  $callback int $chunk_size int $flags

This function will turn output buffering on. While output buffering is active no output is sent from the script, instead the output is stored in an internal buffer. See on exactly what output is affected.

Output buffers are stackable, that is, may be called while another buffer is active. If multiple output buffers are active, output is being filtered sequentially through each of them in nesting order. See for more details. ob_start

See for a detailed description of output buffers.

callback An optional may be specified. It can also be bypassed by passing null. callback``callable

    is invoked when the output buffer is
   flushed (sent), cleaned, or when the output buffer is flushed
   at the end of the script.
  `callback`


   The signature of the  is as follows:
  `callback`


   
   
  ```php

string **** string $buffer int $phase


`buffer`Contents of the output buffer.

`phase`
           Bitmask of
           .
           See 
           for more details.
          PHP_OUTPUT_HANDLER_*
            constants




       If  returns false
       the contents of the buffer are returned.
       See 
       for more details.
      `callback`

> **Waarschuwing:** > Calling any of the following functions from within an output handler
>         will result in a fatal error:
>         , ,
>         , ,
>         , ,
>         .
>        `ob_clean``ob_end_clean``ob_end_flush``ob_flush``ob_get_clean``ob_get_flush``ob_start`


       See 
       and 
       for more details on s (output handlers).
      `callback`

`chunk_size`
       If the optional parameter  is passed,
       the buffer will be flushed after any block of code resulting in output
       that causes the buffer's length to equal
       or exceed .
       The default value  means
       that all output is buffered until the buffer is turned off.
       See  for more details.
      `chunk_size``chunk_size``0`

`flags`
       The  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 the
       .
       See 
       for more details.
      `flags`buffer control flags


       Each flag controls access to a set of functions, as described below:
       
       
      > **Opmerking:** > Prior to PHP 8.4.0, the flags parameter could set
>          the  as well.
>         output handler status flags





return.success


   
  **Voorbeeld: User defined callback function example**

```php
<?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();

?>

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

Voorbeeld: Creating an unerasable output buffer

<?php

ob_start(null, 0, PHP_OUTPUT_HANDLER_STDFLAGS ^ PHP_OUTPUT_HANDLER_REMOVABLE);

?>

ob_get_contents``ob_end_clean``ob_end_flush``ob_implicit_flush``ob_gzhandler``ob_iconv_handler``mb_output_handler``ob_tidyhandler

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