As the page states, "This example opens the current file and iterates over its 
contents line by line."

The whole point of that example is to open the file containing the example code 
and echo each line one by one.

Sorry: my point was not that the example is incorrect, but that it's unclear. Sorry if I didn't express that well.

I believe it could be improved by adding something (for example line numbers) to the output. This would make it clearer that it is the result of the code being run rather than simply a copy of the original source code.

This is what I would suggest:

<?php
$file = new SplFileObject(__FILE__);
foreach ($file as $lineNum=>$line) {
    echo "Line # " . $lineNum . ": " . $line;
}
?>

That is true, the example could be improved to better avoid confusion.

This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation better.