PHP: Why isn't exec() returning output?

Question

I'm writing a PHP script to be used to check for network connections with Linux shell command ping calling it with PHP's exec():

<?php   // Bad IP domain for testing. $domain_bad = "lksjdflksjdf.com";  $ip_address = $domain_bad;  exec("ping -c 1 $domain_bad", $output, $return_var);  var_dump($return_var); echo "return_var is: $return_var" . "\n"; var_dump($output);   exit; ?> 

I'm not getting the output for the error message from ping in $output which is what I'm expecting:

$ php try.php ping: unknown host lksjdflksjdf.com int(2) return_var is: 2 array(0) { } 

If the domain is a good domain, such as yahoo.com, then $output has the output from ping in an array. But if it's an error such as 'ping: unknown host lksjdflksjdf.com' it doesn't get returned to the $output array.

Why is this happening and is there a better method to do this?

Answer 1

You should redirect stderr to stdout.

To do that, change your exec() call like this:

exec("ping -c 1 $domain_bad 2>&1", $output, $return_var); 

More info about 2>&1 meaning here.

Answer 2

If the answer above could not solve your problem, maybe exec() is disabled. You can try to check php.ini file at disable_functions line.