Default parameter values in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are default parameter values in PHP functions?

Default parameter values allow a function to have predefined values for parameters if no argument is passed when the function is called.

beginner

How do you define a default parameter value in a PHP function?

You assign a value to the parameter in the function declaration, like: <code>function greet($name = "Guest") { ... }</code>.

beginner

What happens if you call a PHP function without passing an argument for a parameter that has a default value?

The function uses the default value defined for that parameter.

intermediate

Can parameters with default values be placed before parameters without default values in PHP?

No, parameters with default values must come after parameters without default values to avoid syntax errors.

beginner

Example: What will this PHP code output?<br><pre>function sayHi($name = "Friend") {
  echo "Hi, $name!";
}
sayHi();</pre>

It will output: Hi, Friend! because the function uses the default value for $name when no argument is passed.

What is the correct way to set a default value for a parameter in PHP?

A function example($param) = 10 {}

B function example($param = 10) {}

C function example($param: 10) {}

D function example($param <- 10) {}

In PHP, default values are assigned using the equals sign inside the function parameter list, like $param = 10.

What happens if you call a function with a default parameter but provide an argument?

A The function ignores the argument and uses the default.

B The function throws an error.

C The default value overrides the argument.

D The default value is ignored and the provided argument is used.

When an argument is provided, PHP uses that argument instead of the default value.

Which of these parameter orders is valid in PHP?

A Both B and D

B function test($a, $b = 2) {}

C function test($a = 1, $b) {}

D function test($a = 1, $b = 2) {}

Parameters without default values must come first. So B and D are valid, A is invalid.

What is the output of this code?<br>

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

A Hello, Anna!

B Hello, Guest!

C Hello, !

D Error

Since an argument "Anna" is passed, the function uses it instead of the default.

Can default parameter values be expressions like function calls in PHP?

A Yes, but only if the function is declared as static.

B Yes, any expression is allowed.

C No, only constant values are allowed.

D No, default values must be null.

PHP requires default parameter values to be constant expressions, not function calls or variables.

Explain how default parameter values work in PHP functions and why they are useful.

Think about what happens when you call a function without all arguments.

Describe the rules about the order of parameters with and without default values in PHP function declarations.

Consider what happens if you put a default parameter before a required one.