Why loops are needed in PHP - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print numbers from 1 to 5 using a loop.

PHP

<?php
for ($i = 1; $i [1] 5; $i++) {
    echo $i . "\n";
}
?>

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

A<

B>

C>=

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using < will only print 1 to 4.

Using > or >= will not run the loop correctly.

The loop should run while $i is less than or equal to 5, so using <= with 5 makes it print 1 to 5.

2fill in blank

medium

Complete the code to sum numbers from 1 to 10 using a loop.

PHP

<?php
$sum = 0;
for ($num = 1; $num [1] 10; $num++) {
    $sum += $num;
}
echo $sum;
?>

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

A<=

B<

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using < will exclude 10 from the sum.

Using > or >= will not run the loop correctly.

Using <= ensures the loop includes 10 in the sum.

3fill in blank

hard

Fix the error in the loop condition to print even numbers from 2 to 10.

PHP

<?php
for ($i = 2; $i [1] 10; $i += 2) {
    echo $i . "\n";
}
?>

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

A>

B<

C<=

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using < excludes 10 from the output.

Using > or >= will cause the loop not to run.

Using <= includes 10 in the output, so even numbers 2,4,6,8,10 are printed.

4fill in blank

hard

Fill both blanks to create an associative array of squares for numbers 1 to 5.

PHP

<?php
$squares = [];
for ($i = 1; $i <= 5; $i++) {
    $squares[[1]] = [2];
}
print_r($squares);
?>

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

A$i

B$i * $i

C$i + 1

D$i - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using $i + 1 or $i - 1 will give wrong keys or values.

Swapping keys and values causes incorrect array.

The key should be $i and the value should be $i * $i to store squares.

5fill in blank

hard

Fill all three blanks to create a filtered array of numbers greater than 3 with their squares.

PHP

<?php
$numbers = [1, 2, 3, 4, 5];
$result = [];
foreach ($numbers as [1]) {
    if ([1] > 3) {
        $result[[2]] = [3];
    }
}
print_r($result);
?>

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

A$num

B$num * $num

D$number

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causes errors.

Not filtering numbers greater than 3.

Use $num as the key and $num * $num as the value for numbers greater than 3. The loop variable is $num.

Practice

1. Why do we use loops in PHP programming?

easy

A. To stop the program from running

B. To store data in variables

C. To create new functions

D. To repeat a block of code multiple times without rewriting it

Solution

1. Step 1: Understand the purpose of loops

   Loops allow repeating the same code many times without writing it again and again.

2. Step 2: Compare other options

   Storing data, creating functions, or stopping programs are not the main reasons for loops.

3. Final Answer:

   To repeat a block of code multiple times without rewriting it -> Option D

4. Quick Check:

   Loops repeat code = D [OK]

Hint: Loops repeat code to avoid rewriting [OK]

Common Mistakes:

• Thinking loops store data
• Confusing loops with functions
• Believing loops stop the program

2. Which of the following is the correct syntax to start a for loop in PHP?

easy

A. for ($i = 0; $i < 5; $i++) {

B. for i = 0 to 5 {

C. loop ($i = 0; $i < 5; $i++) {

D. foreach ($i = 0; $i < 5; $i++) {

Solution

1. Step 1: Identify correct PHP for loop syntax

   PHP uses for ($i = 0; $i < 5; $i++) { to start a for loop.

2. Step 2: Check other options for syntax errors

   Options B, C, and D use incorrect keywords or formats not valid in PHP.

3. Final Answer:

   for ($i = 0; $i < 5; $i++) { -> Option A

4. Quick Check:

   PHP for loop syntax = A [OK]

Hint: PHP for loops use semicolons and parentheses [OK]

Common Mistakes:

• Using 'loop' instead of 'for'
• Missing semicolons in for loop
• Using 'foreach' incorrectly

3. What will be the output of this PHP code?

$sum = 0;
for ($i = 1; $i <= 3; $i++) {
    $sum += $i;
}
echo $sum;

medium

A. 3

B. 123

C. 6

D. 0

Solution

1. Step 1: Understand the loop iterations

   The loop runs with $i = 1, 2, 3.

2. Step 2: Calculate the sum during each iteration

   sum = 0+1=1, then 1+2=3, then 3+3=6.

3. Final Answer:

   6 -> Option C

4. Quick Check:

   1+2+3 = 6 [OK]

Hint: Add numbers inside loop to get sum [OK]

Common Mistakes:

• Concatenating numbers instead of adding
• Off-by-one errors in loop condition
• Ignoring initial sum value

4. Find the error in this PHP loop code:

for ($i = 0; $i < 5; $i++)
    echo $i

medium

A. Missing semicolon after echo statement

B. Incorrect loop variable name

C. Loop condition should be <= 5

D. for loop cannot be used without braces

Solution

1. Step 1: Check syntax inside the loop

   The echo statement is missing a semicolon at the end.

2. Step 2: Verify other parts of the loop

   Loop variable and condition are correct; braces are optional for single statements.

3. Final Answer:

   Missing semicolon after echo statement -> Option A

4. Quick Check:

   Missing semicolon = C [OK]

Hint: Every PHP statement ends with a semicolon [OK]

Common Mistakes:

• Forgetting semicolons after statements
• Thinking braces are always required
• Changing loop condition unnecessarily

5. You want to print all even numbers from 2 to 10 using a loop in PHP. Which code correctly does this?

hard

A. for ($i = 1; $i <= 10; $i++) { if ($i % 2 == 1) echo $i; }

B. for ($i = 2; $i <= 10; $i += 2) { echo $i . ' '; }

C. while ($i = 2; $i <= 10; $i++) { echo $i; }

D. foreach (range(2, 10) as $i) { echo $i * 2; }

Solution

1. Step 1: Identify correct loop for even numbers

   for ($i = 2; $i <= 10; $i += 2) { echo $i . ' '; } uses a for loop starting at 2, increasing by 2, printing even numbers correctly.

2. Step 2: Check other options for errors

   for ($i = 1; $i <= 10; $i++) { if ($i % 2 == 1) echo $i; } prints odd numbers, C has wrong while syntax, D multiplies numbers incorrectly.

3. Final Answer:

   for ($i = 2; $i <= 10; $i += 2) { echo $i . ' '; } -> Option B

4. Quick Check:

   Increment by 2 prints evens = B [OK]

Hint: Increment by 2 to print even numbers [OK]

Common Mistakes:

• Using wrong loop syntax
• Printing odd numbers by mistake
• Multiplying instead of selecting evens