Result of test, see http://stackoverflow.com/questions/16595

exec

Array
(
    [commandtotest] => umask
    [output] => 0027
    [rc] => 0
)

shell_exec

Array
(
    [commandtotest] => umask
    [output] => 0027

)

backtick

Array
(
    [commandtotest] => umask
    [output] => 0027

)

0027
passthru

Array
(
    [commandtotest] => umask
    [output] =>
    [rc] => 0
)

0027
system

Array
(
    [commandtotest] => umask
    [output] => 0027
    [rc] => 0
)

popen

Array
(
    [commandtotest] => umask
    [handle] => Resource id #7
    [read] => 0027

)

0027 command returned 0
proc_open

Array
(
    [commandtotest] => umask
    [descriptorspec] => Array
        (
            [0] => Array
                (
                    [0] => pipe
                    [1] => r
                )

            [1] => Array
                (
                    [0] => pipe
                    [1] => w
                )

            [2] => Array
                (
                    [0] => file
                    [1] => /tmp/error-output.txt
                    [2] => a
                )

        )

    [cwd] => /tmp
    [env] => Array
        (
            [some_option] => aeiou
        )

    [process] => Resource id #11
    [pipes] => Array
        (
            [0] => Resource id #9
            [1] => Resource id #10
        )

    [return_value] => 0
)

Array
(
    [programexe] => umask
)

PCNTL functions not available on this PHP installation