How to retrieve PHP exec() error responses?

This worked for me in several scenarios:

 ob_start();
 exec($cmd . " 2>&1", $output);
 $result = ob_get_contents();
 ob_end_clean();
 var_dump($output);

The space between " 2 is important

The $output parameter does not appear to work if the calling program spits output to STDERR.

A better way to handle this is to redirect the output from exec to a file and then display the contents of that file if there is an error condition.

If $cmd holds the exec command add something like this:

$cmd.=" > $error_log 2>&1"

Then examine the contents of the filespec in $error_log for detailed info on why the command failed.

Also note that if you fork this off with a & at the end of the command, an immediate check of the contents of $error_log may not reveal the log information - the script may check/process the file before the OS has finished.

The following code will capture both the normal output (from StdOut) and the error output (from SdtErr).

exec('ln -s ' . PLUGIN_DIR . '/.htaccess ' . ABSPATH . '/.htaccess 2>&1',$output);
var_dump($output);