Variables in shell_exec() script

Question

Is there any possible way to make this simple script function properly?

<?php
$hi = "echo hi";
shell_exec($hi);
echo "<pre>$output</pre>";
?>

please help me out?

Answer 1

$hi = "echo hi";
# the result needs to be assigned to $output before using it
$output = shell_exec($hi);
echo "<pre>$output</pre>";

Answer 2

Sure just assign the variable.

<?php
$hi = "echo hi";
$output = shell_exec($hi);
echo "<pre>$output</pre>";
?>