Anonymous function syntax in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an anonymous function in PHP?

An anonymous function is a function without a name. It can be stored in a variable and used like any other function.

beginner

How do you declare an anonymous function in PHP?

Use the function keyword without a name, followed by parentheses and curly braces. Example: $fn = function() { echo 'Hi'; };

intermediate

How can you pass variables from the parent scope into an anonymous function?

Use the <code>use</code> keyword to import variables. Example: <code>$msg = 'Hello'; $fn = function() use ($msg) { echo $msg; };</code>

beginner

Can anonymous functions in PHP be assigned to variables and called later?

Yes. You assign the anonymous function to a variable and call it using parentheses. Example: $fn = function() { echo 'Hi'; }; $fn();

intermediate

What is a common use case for anonymous functions in PHP?

They are often used as callbacks, for example in array functions like array_map or usort, to define small pieces of code inline.

How do you declare an anonymous function in PHP?

A function() { /* code */ }

B def function() { /* code */ }

C function myFunc() { /* code */ }

D lambda() => { /* code */ }

In PHP, anonymous functions are declared using the function keyword without a name, like function() { /* code */ }.

How do you pass a variable from outside into an anonymous function in PHP?

A Using the global keyword

B By declaring it inside the function

C You cannot pass variables into anonymous functions

D Using the use keyword

You use the use keyword to import variables from the parent scope into the anonymous function.

Which of these is a valid way to call an anonymous function stored in a variable $fn?

A $fn.call();

B call $fn();

C $fn();

D call_function($fn);

You call an anonymous function stored in a variable by adding parentheses after the variable name: $fn();

What is a common use of anonymous functions in PHP?

A Writing long scripts

B Using as callbacks in functions like array_map

C Defining class methods

D Replacing all named functions

Anonymous functions are often used as callbacks, for example in array_map or usort.

Can anonymous functions in PHP have parameters?

A Yes, just like normal functions

B No, they cannot have parameters

C Only one parameter is allowed

D Parameters must be global variables

Anonymous functions can have parameters just like normal functions.

Explain how to create and use an anonymous function in PHP, including how to pass external variables into it.

Think about the function keyword without a name and the use keyword.

Describe a practical example where anonymous functions are useful in PHP programming.

Consider functions like array_map or usort.