What are the potential consequences of using a string as a function in PHP?

Using a string as a function in PHP can lead to security vulnerabilities such as code injection attacks. To prevent this, it is important to validate and sanitize user input before using it as a function name.

// Example of how to validate and sanitize user input before using it as a function name
$functionName = $_POST['function_name'];

// Check if the function name is valid
if (function_exists($functionName)) {
    // Call the function if it exists
    $result = $functionName();
} else {
    // Handle invalid function name
    echo "Invalid function name";
}