php execute linux shell command

• exec : returns the last line of the output by default, but can provide all output as an array specifed as the second parameter.
• shell_exec : returns all of the output stream as a string. ¹
• system() : displays output directly without using echo or print. ²
• passthru() : when the output from the Unix command is binary data ³
• proc_open(): proc_open — Execute a command and open file pointers for input/output ⁴

The error data is output from the target program’s STDERR stream. You can get access to the error data through the normal returned string from shell_exec() by appending 2>&1 to the command, which will redirect STDERR to STDOUT, the stream that you are currently seeing. ⁵

var_dump(shell_exec("ffmpeg -i /var/www/html/sitedomain/httpdocs/tmp/ebev1177.mp4 2>&1"));

$cwd='/tmp';
$descriptorspec = array(
//	0 => array("pipe", "r"),
	1 => array("pipe", "w"),
	2 => array("pipe", "w") );

$process = proc_open("php1 -v", $descriptorspec, $pipes, $cwd);
echo "stdout\n";

$stdout = stream_get_contents($pipes[1]);
var_dump($stdout); 
fclose($pipes[1]);

echo "stderr\n";
$stderr = stream_get_contents($pipes[2]);
var_dump($stderr);
fclose($pipes[2]);