What are the differences between using system, exec, and passthru in PHP for executing external commands?

When executing external commands in PHP, there are several functions available such as system, exec, and passthru. The main differences between these functions lie in how they handle the output of the command and return values. - The system function is used to execute a command and display the output directly to the browser or console. It returns the last line of the output. - The exec function is used to execute a command and store the output in an array. It returns the last line of the output. - The passthru function is used to execute a command and display the output directly to the browser or console. It returns the exit code of the command. Here is an example PHP code snippet that demonstrates the differences between using system, exec, and passthru:

// Using system
$output = system('ls -l');
echo "System Output: $output\n";

// Using exec
exec('ls -l', $output);
echo "Exec Output: " . implode("\n", $output) . "\n";

// Using passthru
$exit_code = passthru('ls -l');
echo "Passthru Exit Code: $exit_code\n";