How can PHP developers ensure security and efficiency when implementing a custom template system in their projects?

To ensure security and efficiency when implementing a custom template system in PHP projects, developers should sanitize user input to prevent XSS attacks and template injection vulnerabilities. Additionally, they should cache compiled templates to improve performance and reduce the load on the server.

// Sanitize user input before using it in the template
$user_input = htmlspecialchars($_POST['input']);

// Cache compiled templates to improve performance
$compiled_template = 'path/to/cache/' . md5($template_file) . '.php';
if (!file_exists($compiled_template)) {
    // Compile the template and save it to the cache
    file_put_contents($compiled_template, compile_template($template_file));
}

// Function to compile the template
function compile_template($template_file) {
    // Code to compile the template goes here
}