How to clear previously echoed items in PHP

In php, is there any way to clear/remove all previously echoed or printed items?

For example:

<?php

echo 'a';
print 'b';

// some statement that removes all printed/echoed items

echo 'c';

// the final output should be equal to 'c', not 'abc'

?>

My script uses the include function. The included files are not supposed to echo anything. Just in case someone (ex = hacker) tries, I need a way to remove.

Solution 1:

<?php

ob_start();
echo 'a';
print 'b';

// some statement that removes all printed/echoed items
ob_end_clean();

echo 'c';

// the final output is equal to 'c', not 'abc'

?>

Output buffering functions

The output buffering functions are also useful in hackery to coerce functions that only print to return strings, ie.

<?php
ob_start();
var_dump($myVar);
$data = ob_get_clean();
// do whatever with $data
?>

Solution 2:

while @monoxide is right, its better to find more intuitive ways of doing the same. e.g.:

<?php
$val_to_print = $a;
if( $need_to_change==true ) 
    $val_to_print = $b;
// when you are sure you won't have to change again...
echo $val_to_print;
?>

Cheers,

jrh