Output Buffering Page 3

With PHP3, all of the content produced
by echo () or print() was sent directly to the server. In PHP4, an
intermediate storage layer makes it possible to defer the sending the Web
server’s output flow. To do this, features so new they have yet to be documented, are available:

• ob_start(): activates
  output buffering

• ob_end_flush(): sends the
  contents of the output buffer and deactivates buffering

• ob_end_clean(): empties the
  output buffer and deactivates buffering

• ob_get_contents(): returns
  the output buffer contents

This functionality makes it possible to prepare the
contents displayed via complex processes requiring several
database queries, for example, and the sending of results only when all of
the queries have been carried out successfully. In the opposite case, users
can empty the output buffer contents and display an error message in its
place. The example below shows a typical case of how these functionalities
are used: