PHP: exec command to get std errors

By appending 2>&1 at the end of the command will redirect errors from stderr to stdout.
Example:
If you run a simple command like cc at the command prompt, you would get the output as following

 $ cc  
 i686-apple-darwin10-gcc-4.2.1: no input files  
 $  

If u run the same command using PHP exec command

 $cmd = "cc";  
 exec($cmd,$out);  
 print_r($out);  

The output would be and empty array:

 Array ( )  

So, In order to get the error string as well, we need to append 2>&1

 $cmd = "cc 2>&1";  
 exec($cmd,$out);  
 print_r($out);  

The output will print:

 Array ( [0] => i686-apple-darwin10-gcc-4.2.1: no input files )