PHP get output stream or just echo

Question

What would be the differnce in php command line app of just echoing or printf etc some string as opposed to getting sdtout stream and writing to it i.e.

$stdout = fopen('php://stdout', 'w');

Answer 1

The first thing that comes to mind for me is output buffering. echo and print interface with the output buffering mechanism, but directly writing to stdout bypasses it.

Consider this script:

<?php
$stdout = fopen('php://stdout', 'w');
ob_start();
        echo "echo output\n";
        fwrite($stdout, "FWRITTEN\n");
        echo "Also echo\n";
$out = ob_get_clean();
echo $out;

which outputs:

FWRITTEN
echo output
Also echo

which demonstrates that echo is buffered, and fwrite is not.

Answer 2

The difference is that echo writes to php://output which is the output buffer stream. However, php://stdout gives you direct access to the processes' output stream which is unbuffered.

Further information regarding streams can be found in the manual: http://www.php.net/manual/en/wrappers.php.php