What are common issues when using PHP to execute shell commands on a Windows server?

Common issues when using PHP to execute shell commands on a Windows server include problems with escaping special characters, handling paths with spaces, and dealing with different command line syntax compared to Unix-based systems. To solve these issues, it's recommended to use the `escapeshellarg()` function to properly escape command arguments and paths, and to use double quotes around paths with spaces.

$command = 'dir "C:\\Program Files"';
$escaped_command = escapeshellarg($command);
$output = shell_exec($escaped_command);
echo $output;