Regarding swbrown's comment...you need to use an output buffer if you don't want the data displayed.

For example:
ob_start();
passthru("<i>command</i>");
$var = ob_get_contents();
ob_end_clean(); //Use this instead of ob_flush()

This gets all the output from the command, and exits without sending any data to stdout.

Note to Paul Giblock: the command *is* run through the shell.
You can verify this on any Linux system with

<?php
passthru ('echo $PATH');
?>

You'll get the content of the PATH environment variable, not the string $PATH.

If you are using passthru() to download files (for dynamically generated content or something outside webserver root) using similar code:

header("Content-Type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"myfile.zip\"");
header("Content-Length: 11111");
passthru("cat myfile.zip",$err);

and your download goes fine, but subsequent downloads / link clicks are screwed up, with headers and binary data being all over the website, try putting

exit();

after the passthrough. This will exit the script after the download is done and will not interfere with any future actions.

if you have problems with passthru("docker-compose ...bash") losing interactive shell size information, try using proc_open instead, for some reason docker-compose bash knows the size of the outer terminal when i use use proc_open, but loses that information when i use passthru,

eg i replaced
<?php
passthru("docker-compose -f docker-compose.yml bash",$ret);
?>
with
<?php
$empty1=array();
$empty2=array();
$proc=proc_open("docker-compose -f docker-compose.yml bash",$empty1,$empty2 );
$ret = proc_close($proc);
?>

and suddenly docker-compose bash knew my terminal size :)

Remember to use the full path (IE '/usr/local/bin/foo' instead of 'foo') when using passthru, otherwise you'll get an exit code of 127 (command not found).

I dunno if anyone else might find this useful, but when I was trying to use the passthru() command on Suse9.3 I was having no success with the command:

$command = 'gdal_translate blahahahaha';

passthru($command);

It only worked once I put:

$command = '/usr/bin/local/gdal_translate blalalala';

passthru($command);

To capture the output of a command in a string without using output buffer functions, use shell_exec()

I was trying to implement a system that allows running arbitrary CLI commands with parameters, but I kept running into the issues with user prompts from the command as they would let execution hang. The solution is simple: just use passthru() as it outputs everything and correctly handles user prompts out of the box.

PHP's program-execution commands fail miserably when it comes to STDERR, and the proc_open() command doesn't work all that consistently in non-blocking mode under Windows.

This command, although useful, is no different. To form a mechanism that will see/capture both STDOUT and STDERR output, pipe the command to the 'tee' command (which can be found for Windows), and wrap the whole thing in output buffering.

Dustin Oprea

If you have chrooted apache and php, you will also want to put /bin/sh into the chrooted environment. Otherwise, the exec() or passthru() will not function properly, and will produce error code 127, file not found.

Zak Estrada
14-Dec-2004 11:21 
Remember to use the full path (IE '/usr/local/bin/foo' instead of 'foo') when using passthru, otherwise you'll get an exit code of 127 (command not found).

Remember, you'll also get this error if your file does not have executable permission.

passthru() seems absolutely determined to buffer output no matter what you do, even with ob_implicit_flush().  The solution seems to be to use popen() instead.

I wrote function, that gets proxy server value from the Internet Explorer (from
registry). It was tested in Windows XP Pro

(Sorry for my English)

<?php
function getProxyFromIE()
{
        exec("reg query \"HKEY_CURRENT_USER\Software\Microsoft".
        "\Windows\CurrentVersion\Internet Settings\" /v ProxyEnable",
        $proxyenable,$proxyenable_status);

        exec("reg query \"HKEY_CURRENT_USER\Software\Microsoft".
        "\Windows\CurrentVersion\Internet Settings\" /v ProxyServer",
        $proxyserver);

        if($proxyenable_status!=0)
        return false; #Can't access the registry! Very very bad...
        else
        {
        $enabled=substr($proxyenable[4],-1,1);
        if($enabled==0)
        return false;
        else
        {
        $proxy=ereg_replace("^[ \t]{1,10}ProxyServer\tREG_SZ[ \t]{1,20}","",
        $proxyserver[4]);

        if(ereg("[\=\;]",$proxy))
        {
             $proxy=explode(";",$proxy);
             foreach($proxy as $i => $v)
             {
                   if(ereg("http",$v))
                   {
                   $proxy=str_replace("http=","",$v);
                   break;
                   }
             }
             if(@!ereg("^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\:".
             "[0-9]{1,5}$",$proxy))
             return false;
             else
             return $proxy;
        }
        else
        return $proxy;
        }

        }
}
?>
Note, that this function returns FALSE if proxy is disabled in Internet
Explorer. This function returns ONLY HTTP proxy server.

Usage:
<?php
$proxy=getProxyFromIE();
if(!$proxy)
echo "Can't get proxy!";
else
echo $proxy;
?>

The documention does not mention that passthru() will only display standard output and not standard error.

If you are running a script you can pipe the STDERR to STDOUT by doing 

exec 2>&1

Eg. the script below will actually print something with the passthru() function...

#!/bin/sh
exec 2>&1
ulimit -t 60
cat nosuchfile.txt

Thought it might beuseful to note the passthru seems to supress error messages whilst being run in Dos on Windows (test on NT).

To show FULL raw output including errors, use system().