Nested conditional execution in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested if-else blocks

What is the output of this PHP code snippet?

PHP

<?php
$score = 75;
if ($score >= 90) {
    echo "Grade: A";
} else {
    if ($score >= 70) {
        echo "Grade: B";
    } else {
        echo "Grade: C";
    }
}
?>

A No output

B Grade: A

C Grade: C

D Grade: B

💡 Hint

Check the first condition and then the nested condition inside the else block.

The score 75 is not >= 90, so the first if fails. Then the nested if checks if score >= 70, which is true, so it prints 'Grade: B'.

❓ Predict Output

intermediate

Nested condition with logical operators

What will this PHP code output?

PHP

<?php
$age = 20;
$hasID = true;
if ($age >= 18) {
    if ($hasID) {
        echo "Access granted";
    } else {
        echo "ID required";
    }
} else {
    echo "Access denied";
}
?>

A No output

B ID required

C Access granted

D Access denied

💡 Hint

Check both conditions inside the nested if.

Age is 20 (>=18) and hasID is true, so both conditions pass and 'Access granted' is printed.

🔧 Debug

advanced

Identify the error in nested condition

What error does this PHP code produce when run?

PHP

<?php
$number = 10;
if ($number > 0) {
    if $number < 20 {
        echo "Number is between 1 and 19";
    }
}
?>

A Parse error: syntax error, unexpected '$number' (T_VARIABLE)

B No output

C Output: Number is between 1 and 19

D Fatal error: Uncaught Error: Undefined variable

💡 Hint

Check the syntax of the nested if statement.

The nested if is missing parentheses around the condition, causing a syntax error.

❓ Predict Output

advanced

Output of nested if-elseif-else

What is the output of this PHP code?

PHP

<?php
$val = 15;
if ($val > 20) {
    echo "Greater than 20";
} elseif ($val > 10) {
    if ($val % 2 == 0) {
        echo "Even and greater than 10";
    } else {
        echo "Odd and greater than 10";
    }
} else {
    echo "10 or less";
}
?>

A Odd and greater than 10

B Even and greater than 10

C Greater than 20

D 10 or less

💡 Hint

Check the elseif condition and then the nested if inside it.

15 is not > 20, but is > 10. 15 % 2 is 1 (odd), so it prints 'Odd and greater than 10'.

🧠 Conceptual

expert

Understanding nested conditional flow

Consider this PHP code snippet. What will be the value of $result after execution?

PHP

<?php
$a = 5;
$b = 10;
if ($a > $b) {
    if ($a - $b > 3) {
        $result = 'A';
    } else {
        $result = 'B';
    }
} else {
    if ($b - $a > 3) {
        $result = 'C';
    } else {
        $result = 'D';
    }
}
?>

A "B"

B "C"

C "A"

D "D"

💡 Hint

Compare values of $a and $b and check the nested conditions carefully.

Since $a (5) is not greater than $b (10), the else block runs. Then $b - $a = 5, which is > 3, so $result is set to 'C'.

Practice

1.

What does nested conditional execution mean in PHP?

easy

A. Running PHP code without any conditions

B. Writing multiple if statements one after another without nesting

C. Using only one if statement without any else

D. Using an if or else statement inside another if or else block

Solution

1. Step 1: Understand conditional statements

   Conditional statements like if and else let the program choose actions based on conditions.

2. Step 2: Define nested conditionals

   Nested conditionals mean placing one conditional inside another to check multiple conditions step-by-step.

3. Final Answer:

   Using an if or else statement inside another if or else block -> Option D

4. Quick Check:

   Nested conditionals = condition inside condition [OK]

Hint: Look for conditions placed inside other conditions [OK]

Common Mistakes:

• Thinking multiple separate ifs are nested
• Confusing nested with chained conditions
• Ignoring the inner condition placement

2.

Which of the following is the correct syntax for nested if statements in PHP?

<?php
if ($a > 0) {
    if ($b < 10) {
        echo "Inside nested if";
    }
}
?>

easy

A. Using elseif instead of nested if

B. Correct syntax with braces and proper nesting

C. Missing braces around inner if block

D. Using parentheses incorrectly around conditions

Solution

1. Step 1: Check braces usage

   Both outer and inner if statements have braces to define their blocks properly.

2. Step 2: Verify condition syntax

   Conditions use parentheses correctly and logical operators are valid.

3. Final Answer:

   Correct syntax with braces and proper nesting -> Option B

4. Quick Check:

   Proper braces and nesting = correct syntax [OK]

Hint: Always use braces {} for nested blocks [OK]

Common Mistakes:

• Omitting braces causing syntax errors
• Misplacing parentheses in conditions
• Confusing elseif with nested if

3.

What will be the output of the following PHP code?

<?php
$x = 5;
$y = 8;
if ($x > 3) {
    if ($y < 10) {
        echo "A";
    } else {
        echo "B";
    }
} else {
    echo "C";
}
?>

medium

A. No output

B. B

C. A

D. C

Solution

1. Step 1: Evaluate outer if condition

   $x = 5, which is greater than 3, so the outer if block runs.

2. Step 2: Evaluate inner if condition

   $y = 8, which is less than 10, so the inner if block runs and prints "A".

3. Final Answer:

   A -> Option C

4. Quick Check:

   5 > 3 and 8 < 10 = A [OK]

Hint: Check outer condition first, then inner [OK]

Common Mistakes:

• Ignoring inner condition result
• Confusing else blocks
• Assuming else runs when condition is true

4.

Find the error in this nested conditional PHP code:

<?php
$a = 10;
if ($a > 5)
    if ($a < 15)
        echo "Inside nested if";
    else
        echo "Outside nested if";
?>

medium

A. Missing braces causing else to pair with wrong if

B. Incorrect comparison operators

C. Echo statements missing semicolons

D. Variable $a not defined

Solution

1. Step 1: Analyze if-else pairing without braces

   Without braces, the else pairs with the nearest if, which is the inner one.

2. Step 2: Understand the problem

   This can cause confusion or unexpected behavior because the outer if has no else block explicitly.

3. Final Answer:

   Missing braces causing else to pair with wrong if -> Option A

4. Quick Check:

   Braces needed to clarify else pairing [OK]

Hint: Always use braces to avoid else ambiguity [OK]

Common Mistakes:

• Assuming else pairs with outer if
• Ignoring indentation as syntax guide
• Missing semicolons (not the issue here)

5.

Given the following PHP code, what will be the output?

<?php
$score = 75;
if ($score >= 90) {
    echo "Grade A";
} else {
    if ($score >= 75) {
        if ($score >= 80) {
            echo "Grade B+";
        } else {
            echo "Grade B";
        }
    } else {
        echo "Grade C";
    }
}
?>

hard

A. Grade B

B. Grade B+

C. Grade C

D. Grade A

Solution

1. Step 1: Check first condition

   $score = 75, which is not >= 90, so skip first if block.

2. Step 2: Check second condition

   $score >= 75 is true, so enter second if.

3. Step 3: Check nested condition inside second if

   $score >= 80 is false (75 < 80), so execute else and print "Grade B".

4. Final Answer:

   Grade B -> Option A

5. Quick Check:

   75 >= 75 but < 80 = Grade B [OK]

Hint: Follow conditions top-down carefully [OK]

Common Mistakes:

• Confusing >= 75 and >= 80 checks
• Skipping nested else block
• Assuming 75 is >= 80