Why global state is dangerous in PHP - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a global variable in PHP.

PHP

<?php
$counter = 0;
function increment() {
    global [1];
    $counter++;
}
?>

Drag options to blanks, or click blank then click option'

A$counter

B$count

C$globalCounter

D$var

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to use the global keyword.

Using a different variable name inside the function.

In PHP, to access a global variable inside a function, you must declare it with the global keyword followed by the variable name.

2fill in blank

medium

Complete the code to modify a global variable inside a function.

PHP

<?php
$score = 10;
function addPoints() {
    global [1];
    $score += 5;
}
?>

Drag options to blanks, or click blank then click option'

A$points

B$total

C$score

D$value

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name inside the function.

Not declaring the variable as global.

You must declare the global variable inside the function to modify it. Here, $score is the global variable.

3fill in blank

hard

Fix the error in the code to correctly access the global variable inside the function.

PHP

<?php
$count = 5;
function showCount() {
    echo [1];
}
showCount();
?>

Drag options to blanks, or click blank then click option'

A$count

Bglobal $count

Cglobal $GLOBALS['count']

D$GLOBALS['count']

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to echo the variable without declaring it global.

Using 'global $count' inside echo statement.

To access a global variable inside a function without declaring it global, use the $GLOBALS array with the variable name as key.

4fill in blank

hard

Fill both blanks to create a function that modifies a global variable safely.

PHP

<?php
$visits = 0;
function visitPage() {
    [1] $visits;
    $visits [2] 1;
}
?>

Drag options to blanks, or click blank then click option'

Aglobal

B+=

C-=

D*=

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to declare the variable as global.

Using the wrong operator to increment.

Declare the variable as global inside the function, then use the += operator to increase its value by 1.

5fill in blank

hard

Fill all three blanks to demonstrate why global state can cause bugs in PHP.

PHP

<?php
$flag = false;
function toggleFlag() {
    [1] $flag;
    if ($flag [2] false) {
        $flag [3] true;
    } else {
        $flag = false;
    }
}
?>

Drag options to blanks, or click blank then click option'

Aglobal

B==

C=

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using assignment operator instead of comparison in the if condition.

Not declaring the variable as global.

Declare $flag as global to access it. Use == to check if it is false, then assign true to toggle it. This shows how global state can be changed unexpectedly.