<?php

$descriptors = array(
   0 => array("pipe", "r"),
   1 => array("pipe", "w")
);

$php = proc_open('php', $descriptors, $pipes);

stream_set_blocking($pipes[1], 0);

fwrite($pipes[0], '<?php echo \'foo\'; fopen(\'php://stdout\', \'w\'); echo \'bar\'; ?>');
fclose($pipes[0]);

$null = null;

$select = array($pipes[1]);

while (feof($pipes[1]) === false)
{
    if (stream_select($select, $null, $null, null))
    {
        var_dump(stream_get_contents($pipes[1]));
    }
}