How to create optional arguments in PHP ?

In PHP, we can create optional arguments in a function by assigning a default value to the parameter. If the argument is not passed while calling the function, the default value will be used.

Here's an example:

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

greet(); // Output: Hello, Guest!
greet("John"); // Output: Hello, John!

In the above example, the greet() function has an optional parameter $name with a default value of "Guest". If the function is called without passing any argument, the default value will be used. If an argument is passed, it will override the default value.

We can also have multiple optional parameters in a function. Here's an example:

function calculate($num1, $num2 = 0, $operator = "+") {
  switch($operator) {
    case "+":
      return $num1 + $num2;
    case "-":
      return $num1 - $num2;
    case "*":
      return $num1 * $num2;
    case "/":
      return $num1 / $num2;
    default:
      return "Invalid operator";
  }
}

echo calculate(10); // Output: 10
echo calculate(10, 5); // Output: 15
echo calculate(10, 5, "-"); // Output: 5

In the above example, the calculate() function has three parameters - $num1, $num2, and $operator. $num2 and $operator are optional parameters with default values of 0 and "+" respectively. If the function is called without passing $num2 and $operator, their default values will be used. If only $num2 is passed, $operator will have its default value. If both $num2 and $operator are passed, they will override their default values.