PHP

What are the Default Arguments in PHP ? Give Example

Default arguments (or default parameters) in PHP allow you to assign a default value to a function parameter. If the caller does not provide a value for that parameter, PHP automatically uses the default value. This makes functions more flexible, easier to use, and reduces the need for overloaded functions.

What Are Default Arguments?

Default arguments are predefined parameter values used when no value is passed during a function call.

Example:

function greet($name = "Guest") {
    echo "Hello, $name!";
}

If no argument is passed, "Guest" is used automatically.

Syntax

function functionName($param1 = defaultValue, $param2 = defaultValue) {
    // code execution
}

Example 1: Basic Default Argument

function welcome($user = "Visitor") {
    echo "Welcome, $user!";
}

welcome();            // Output: Welcome, Visitor!
welcome("Sagar");     // Output: Welcome, Sagar!

Example 2: Default Argument in Calculations

function multiply($a, $b = 2) {
    return $a * $b;
}

echo multiply(5);     // Output: 10 (5 * 2)
echo multiply(5, 4);  // Output: 20

Example 3: Multiple Default Arguments

function orderPizza($size = "Medium", $crust = "Regular") {
    echo "Order: $size Pizza with $crust Crust";
}

orderPizza();

Example 4: Using Non-Default + Default Together

Important rule:
➡ Default arguments must come after non-default arguments

function introduce($name, $greeting = "Hello") {
    echo "$greeting, $name!";
}

introduce("Sagar");

❌ Wrong:

function intro($greeting = "Hello", $name) { }

Why Use Default Arguments?

Makes functions easier to call
Avoids multiple function overloads
Makes code cleaner & more flexible
Handles optional parameters gracefully
Reduces error chances when arguments are missing

Real-World Use Cases

✔ API functions with optional filters
✔ Pagination functions (e.g., default page = 1)
✔ Message or notification systems
✔ Utility functions like string or math helpers