Global keyword behavior in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the global keyword do in PHP?

It allows a function to access variables defined outside its scope, specifically global variables, by linking the local variable to the global one.

intermediate

How do you access a global variable inside a function without using the global keyword?

You can access global variables using the $GLOBALS array, for example: $GLOBALS['varName'].

beginner

What happens if you modify a global variable inside a function without declaring it global?

The function creates a new local variable with the same name, leaving the global variable unchanged.

beginner

Example: What will this code output?<br><pre> $x = 5;<br>function test() {<br>  global $x;<br>  $x = 10;<br>}<br>test();<br>echo $x;</pre>

It will output 10 because the global keyword links the local $x to the global $x, so the change affects the global variable.

intermediate

Why is using the global keyword sometimes discouraged?

Because it can make code harder to understand and debug by creating hidden dependencies between functions and global state. It's often better to pass variables as parameters.

What does the global keyword do inside a PHP function?

A Links a local variable to a global variable of the same name

B Creates a new local variable

C Deletes a global variable

D Makes a variable private

The global keyword links the local variable to the global variable with the same name.

How can you access a global variable inside a function without using global?

A Using <code>const</code> keyword

B Using <code>static</code> keyword

C Using the <code>$GLOBALS</code> array

D You cannot access it

The $GLOBALS array holds all global variables and can be used inside functions.

What will happen if you assign a value to a global variable inside a function without declaring it global?

A The global variable changes

B The variable becomes constant

C An error occurs

D A new local variable is created

Without global, the assignment creates a new local variable.

Which of these is a downside of using the global keyword?

A It creates hidden dependencies and can make debugging harder

B It improves performance

C It makes code easier to read

D It automatically documents code

Using global can hide dependencies and make code harder to maintain.

Given $a = 3; outside a function, what will echo $a; output after this function?<br>

function change() { global $a; $a = 7; } change();

A 3

B 7

C Error

D Nothing

The global keyword links the function's $a to the global $a, so the value changes to 7.

Explain how the global keyword works in PHP functions and why it is used.

Think about variable scope and how functions normally can't see outside variables.

Describe the alternatives to using the global keyword for accessing global variables inside functions.

Consider safer ways to share data between functions.