ob_get_clean in PHP

ob_get_clean — Get current buffer contents and delete current output buffer
Syntax: string ob_get_clean ( void )
Gets the current buffer contents and delete current output buffer.
ob_get_clean() essentially executes both ob_get_contents() and ob_end_clean().
The output buffer must be started by ob_start() with PHP_OUTPUT_HANDLER_CLEANABLE flag. Otherwise ob_get_clean() will not work.

Return Values:Returns the contents of the output buffer and end output buffering. If output buffering isn't active then FALSE is returned.
Example #1
<?php
ob_start();
echo "Hello World";
$out = ob_get_clean();
$out = strtolower($out);
var_dump($out);
?>
Output:string(11) "hello world"