If statement execution flow in PHP - Mini Project: Build & Apply

If Statement Execution Flow in PHP

📖 Scenario: You are creating a simple program to check the weather temperature and give advice on what to wear.

🎯 Goal: Build a PHP script that uses if statements to decide what message to show based on the temperature.

📋 What You'll Learn

Create a variable called $temperature with the exact value 15.

Create a variable called $cold_threshold with the exact value 10.

Use an if statement to check if $temperature is less than $cold_threshold.

If true, set a variable $message to 'It is cold, wear a jacket.'.

Otherwise, set $message to 'The weather is nice, no jacket needed.'.

Print the $message variable.

💡 Why This Matters

🌍 Real World

Checking conditions like weather temperature helps apps give useful advice, like what clothes to wear.

💼 Career

Understanding if statements is essential for any programming job because it helps programs make decisions.

1

Set the temperature variable

Create a variable called $temperature and set it to the number 15.

PHP

<?php

// Create a variable called $temperature and set it to 15
// Your code here

Hint

Use the $ sign to create variables in PHP.

2

Set the cold threshold variable

Create a variable called $cold_threshold and set it to the number 10.

PHP

<?php

$temperature = 15;

// Create a variable called $cold_threshold and set it to 10
// Your code here

Hint

Remember to use $ before variable names in PHP.

3

Write the if statement to check temperature

Write an if statement that checks if $temperature is less than $cold_threshold. If true, set $message to 'It is cold, wear a jacket.'. Otherwise, set $message to 'The weather is nice, no jacket needed.'.

PHP

<?php

$temperature = 15;
$cold_threshold = 10;

// Write an if statement to set $message based on temperature
// Your code here

Hint

Use if (condition) { ... } else { ... } structure in PHP.

4

Print the message

Write a print statement to display the $message variable.

PHP

<?php

$temperature = 15;
$cold_threshold = 10;

if ($temperature < $cold_threshold) {
    $message = 'It is cold, wear a jacket.';
} else {
    $message = 'The weather is nice, no jacket needed.';
}

// Print the $message variable
// Your code here

Hint

Use print($message); to show the message on the screen.

Practice

1. What does an if statement do in PHP?

easy

A. It defines a function.

B. It repeats code multiple times.

C. It runs code only if a condition is true.

D. It stops the program immediately.

Solution

1. Step 1: Understand the purpose of an if statement

   An if statement checks a condition and runs code only if that condition is true.

2. Step 2: Compare with other options

   Repeating code is done by loops, functions define reusable code, and stopping the program is done by exit or die.

3. Final Answer:

   It runs code only if a condition is true. -> Option C

4. Quick Check:

   If statement = runs code if true [OK]

Hint: If checks condition; runs code only when true [OK]

Common Mistakes:

• Confusing if with loops
• Thinking if defines functions
• Believing if stops the program

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

easy

A. if condition { echo 'Yes'; }

B. if (condition) { echo 'Yes'; }

C. if condition: echo 'Yes'; endif;

D. if [condition] { echo 'Yes'; }

Solution

1. Step 1: Recall PHP if statement syntax

   In PHP, the condition must be inside parentheses and the code block inside curly braces.

2. Step 2: Check each option

   if (condition) { echo 'Yes'; } matches the correct syntax: if (condition) { ... }. if condition { echo 'Yes'; } misses parentheses, C uses alternate syntax but missing parentheses, D uses square brackets which is invalid.

3. Final Answer:

   if (condition) { echo 'Yes'; } -> Option B

4. Quick Check:

   Parentheses around condition = correct syntax [OK]

Hint: Always use parentheses around condition in if [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using square brackets instead of parentheses
• Confusing alternate syntax without proper format

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

$x = 10;
if ($x > 10) {
  echo 'Greater';
} elseif ($x == 10) {
  echo 'Equal';
} else {
  echo 'Less';
}

medium

A. Equal

B. No output

C. Less

D. Greater

Solution

1. Step 1: Evaluate the condition $x > 10

   $x is 10, so $x > 10 is false. The first if block is skipped.

2. Step 2: Check the elseif condition $x == 10

   This condition is true, so it prints 'Equal' and skips the else block.

3. Final Answer:

   Equal -> Option A

4. Quick Check:

   10 == 10 prints Equal [OK]

Hint: Check conditions top to bottom; first true runs [OK]

Common Mistakes:

• Assuming > includes equal
• Ignoring elseif and jumping to else
• Thinking multiple blocks run

4. Find the error in this PHP code:

if $a > 5 {
  echo 'Big';
} else {
  echo 'Small';
}

medium

A. Wrong keyword else

B. Missing semicolon after echo

C. Curly braces not allowed

D. Missing parentheses around condition

Solution

1. Step 1: Check if statement syntax

   In PHP, the condition must be inside parentheses. Here, if $a > 5 is missing parentheses.

2. Step 2: Verify other parts

   Semicolons after echo statements are optional if echo is used as a statement, else keyword is correct, and curly braces are allowed.

3. Final Answer:

   Missing parentheses around condition -> Option D

4. Quick Check:

   Condition must be in parentheses [OK]

Hint: Always put condition inside parentheses in if [OK]

Common Mistakes:

• Forgetting parentheses around condition
• Thinking else keyword is wrong
• Believing semicolon is mandatory after echo

5. Given this PHP code, what will be the output?

$score = 75;
if ($score >= 90) {
  echo 'A';
} elseif ($score >= 80) {
  echo 'B';
} elseif ($score >= 70) {
  echo 'C';
} else {
  echo 'F';
}

hard

A. C

B. A

C. B

D. F

Solution

1. Step 1: Check first condition $score >= 90

   75 is less than 90, so this is false. Skip to next.

2. Step 2: Check second condition $score >= 80

   75 is less than 80, so false again. Skip to next.

3. Step 3: Check third condition $score >= 70

   75 is greater than or equal to 70, so true. It prints 'C' and skips else.

4. Final Answer:

   C -> Option A

5. Quick Check:

   75 >= 70 prints C [OK]

Hint: Check conditions top-down; first true runs [OK]

Common Mistakes:

• Choosing wrong grade for score
• Ignoring elseif order
• Assuming else runs always