Using constants

Constants in PHP are defined using the define() function and are typically used to store values that remain constant throughout the execution of a script. Here's how you can define and use constants in PHP:

// Define a constant
define("MAX_ATTEMPTS", 5);

// Use the constant

echo "Maximum allowed attempts: " . MAX_ATTEMPTS;

In this example:

The define() function is used to create a constant named MAX_ATTEMPTS with a value of 5.
Later, the constant is used within the echo statement to display its value.

Constants are useful for storing values that should not be changed during the execution of the script. They provide a way to make your code more readable and maintainable by giving meaningful names to commonly used values. Additionally, using constants makes it easier to update these values later if needed, as you only need to change the value at the point of declaration.

You can use constants anywhere in your code, including inside functions and classes, as long as they are defined in the global scope or imported into the local scope using the use keyword or the global keyword.

define("MAX_ATTEMPTS", 5);

function login($username, $password) {
if ($attempts >= MAX_ATTEMPTS) {
echo "Maximum login attempts reached.";
return;
}
// Login logic
}

In this example, the constant MAX_ATTEMPTS is used inside the login() function to determine whether the maximum login attempts have been reached.