how to execute php command inside php code example

Example 1: run php script from another php

<?php 
include('log test.php');
$output = shell_exec('php filename.php');
echo "<pre>$output</pre>";

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://localhost/Ia2/Watering/tests/log%20test.php"); //URL of the file
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$output = curl_exec($ch);
curl_close($ch);
echo "<pre>$output</pre>";
?>

Example 2: how to execute cmd command in php

I'm not sure what shell you are going to get with this function, but you can find out like this:

<?php
$cmd = 'set';
echo "<pre>".shell_exec($cmd)."</pre>";
?>

On my FreeBSD 6.1 box I get this:

USER=root
LD_LIBRARY_PATH=/usr/local/lib/apache2:
HOME=/root
PS1='$ '
OPTIND=1
PS2='> '
LOGNAME=root
PPID=88057
PATH=/etc:/bin:/sbin:/usr/bin:/usr/sbin
SHELL=/bin/sh
IFS='     
'

Very interesting.  Note that the PATH may not be as complete as you need.  I wanted to run Ghostscript via ImageMagik's "convert" and ended up having to add my path before running the command:

<?php
$cmd = 'export PATH="/usr/local/bin/"; convert -scale 25%x25% file1.pdf[0] file2.png 2>&1';
echo "<pre>".shell_exec($cmd)."</pre>";
?>

ALSO, note that shell_exec() does not grab STDERR, so use "2>&1" to redirect it to STDOUT and catch it.