Why conditional flow is needed in PHP - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a number is positive.

PHP

<?php
$number = 5;
if ($number [1] 0) {
    echo "Positive number";
}
?>

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

A!=

B<

C==

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' will check for negative numbers.

Using '==' checks for equality, not positivity.

The condition $number > 0 checks if the number is greater than zero, meaning it is positive.

2fill in blank

medium

Complete the code to print 'Even' if the number is even.

PHP

<?php
$number = 4;
if ($number % 2 [1] 0) {
    echo "Even";
}
?>

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

A>

B!=

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' will check for odd numbers instead.

Using '>' or '<' does not correctly check for evenness.

The condition $number % 2 == 0 checks if the remainder when dividing by 2 is zero, meaning the number is even.

3fill in blank

hard

Fix the error in the condition to check if a number is negative.

PHP

<?php
$number = -3;
if ($number [1] 0) {
    echo "Negative number";
}
?>

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

A<

B>

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' checks for positive numbers instead.

Using '==' checks for zero, not negativity.

The condition $number < 0 correctly checks if the number is less than zero, meaning negative.

4fill in blank

hard

Fill both blanks to create a condition that checks if a number is between 1 and 10.

PHP

<?php
$number = 7;
if ($number [1] 1 && $number [2] 10) {
    echo "Number is between 1 and 10";
}
?>

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

A>

B<

C>=

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using only '>' or '<' excludes the boundary numbers.

Mixing up the operators can cause wrong results.

The condition $number >= 1 && $number <= 10 checks if the number is at least 1 and at most 10.

5fill in blank

hard

Fill all three blanks to create a condition that checks if a number is positive, even, and less than 20.

PHP

<?php
$number = 16;
if ($number [1] 0 && $number % 2 [2] 0 && $number [3] 20) {
    echo "Number is positive, even, and less than 20";
}
?>

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

A>

B==

C<

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>=' instead of '>' includes zero, which is not positive.

Using '!=' instead of '==' for evenness checks odd numbers.

Using '>=' instead of '<' for the upper limit includes 20.

The condition checks three things: number greater than zero, number even (remainder zero), and number less than 20.

Practice

1. Why do we need conditional flow in PHP programs?

easy

A. To store data permanently on the server

B. To repeat the same code many times without change

C. To make decisions and run different code based on conditions

D. To create new variables automatically

Solution

1. Step 1: Understand the purpose of conditional flow

   Conditional flow allows a program to choose what code to run based on true or false conditions.

2. Step 2: Compare options with this purpose

   Only To make decisions and run different code based on conditions describes making decisions and running different code based on conditions, which matches the purpose.

3. Final Answer:

   To make decisions and run different code based on conditions -> Option C

4. Quick Check:

   Conditional flow = decision making [OK]

Hint: Conditional flow means choosing code to run based on true/false [OK]

Common Mistakes:

• Confusing conditional flow with loops
• Thinking conditional flow stores data
• Believing conditional flow creates variables

2. Which of the following is the correct syntax for an if statement in PHP?

easy

A. if ($a > $b) { echo 'Yes'; }

B. if $a > $b then echo 'Yes';

C. if ($a > $b) echo 'Yes'

D. if $a > $b { echo 'Yes'; }

Solution

1. Step 1: Recall PHP if statement syntax

   PHP requires parentheses around the condition and curly braces around the code block.

2. Step 2: Check each option for correct syntax

   if ($a > $b) { echo 'Yes'; } uses parentheses and curly braces correctly. if ($a > $b) echo 'Yes' misses semicolon after echo and curly braces, causing syntax error. The other options lack parentheses or use invalid 'then' keyword.

3. Final Answer:

   if ($a > $b) { echo 'Yes'; } -> Option A

4. Quick Check:

   Correct if syntax = if ($a > $b) { echo 'Yes'; } [OK]

Hint: Use parentheses for condition and braces for code block [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using 'then' keyword which PHP does not have
• Missing curly braces for code block

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

$score = 75;
if ($score >= 60) {
    echo 'Pass';
} else {
    echo 'Fail';
}

medium

A. Pass

B. Fail

C. Error

D. No output

Solution

1. Step 1: Evaluate the condition $score >= 60

   The variable $score is 75, which is greater than or equal to 60, so the condition is true.

2. Step 2: Determine which block runs

   Since the condition is true, the code inside the if block runs, printing 'Pass'.

3. Final Answer:

   Pass -> Option A

4. Quick Check:

   75 >= 60 is true, so output = Pass [OK]

Hint: Check if condition is true to pick output [OK]

Common Mistakes:

• Confusing true and false branches
• Assuming code errors without syntax issues
• Ignoring the else block

4. Find the error in this PHP code snippet:

if $age > 18 {
    echo 'Adult';
} else {
    echo 'Minor';
}

medium

A. Missing semicolon after echo statements

B. Missing parentheses around the condition

C. Incorrect use of else keyword

D. Variable $age is not defined

Solution

1. Step 1: Check syntax of if statement

   PHP requires parentheses around the condition in an if statement.

2. Step 2: Identify the missing parentheses

   The code uses if $age > 18 without parentheses, which causes a syntax error.

3. Final Answer:

   Missing parentheses around the condition -> Option B

4. Quick Check:

   if condition needs parentheses [OK]

Hint: Always put parentheses around if conditions [OK]

Common Mistakes:

• Forgetting parentheses in if conditions
• Thinking semicolons are needed after echo inside braces
• Assuming else keyword is wrong

5. You want to write a PHP program that prints 'Good morning' if the hour is less than 12, 'Good afternoon' if the hour is between 12 and 17 (inclusive), and 'Good evening' otherwise. Which conditional flow structure correctly implements this?

hard

A. if ($hour < 12) { echo 'Good morning'; } else if ($hour > 12 && $hour < 17) { echo 'Good afternoon'; } else { echo 'Good evening'; }

B. if ($hour <= 12) { echo 'Good morning'; } else if ($hour < 17) { echo 'Good afternoon'; } else { echo 'Good evening'; }

C. if ($hour < 12) { echo 'Good morning'; } if ($hour >= 12 && $hour <= 17) { echo 'Good afternoon'; } else { echo 'Good evening'; }

D. if ($hour < 12) { echo 'Good morning'; } elseif ($hour <= 17) { echo 'Good afternoon'; } else { echo 'Good evening'; }

Solution

1. Step 1: Understand the conditions for each greeting

   'Good morning' if hour < 12, 'Good afternoon' if 12 ≤ hour ≤ 17, else 'Good evening'.

2. Step 2: Analyze the correct structure

   if ($hour < 12) { echo 'Good morning'; } elseif ($hour <= 17) { echo 'Good afternoon'; } else { echo 'Good evening'; } works perfectly: elseif only runs if hour ≥ 12, and ≤ 17 covers 12 to 17 inclusive without gaps or overlaps.

3. Step 3: Check other structures for errors

   The structure with if ($hour <= 12) for morning misclassifies hour 12. The structure with separate if for afternoon followed by else prints both morning and evening for hour < 12. The structure with else if ($hour > 12 && $hour < 17) excludes 12 and 17 from afternoon.

4. Final Answer:

   if ($hour < 12) { echo 'Good morning'; } elseif ($hour <= 17) { echo 'Good afternoon'; } else { echo 'Good evening'; } -> Option D

5. Quick Check:

   if <12 morning, elseif ≤17 (implies ≥12) afternoon, else evening [OK]

Hint: Check all ranges carefully and use separate ifs if needed [OK]

Common Mistakes:

• Overlapping or missing hour ranges
• Using else if instead of elseif (both work but watch syntax)
• Not including boundary values like 12 or 17 correctly