Switch statement execution in PHP - Mini Project: Build & Apply

Switch statement execution

📖 Scenario: You are creating a simple program to display the day of the week based on a number input. This is like a small calendar helper that tells you the name of the day when you enter a number from 1 to 7.

🎯 Goal: Build a PHP program that uses a switch statement to print the correct day name for a given number.

📋 What You'll Learn

Create a variable called dayNumber with a value from 1 to 7

Create a variable called defaultDay with the value 'Invalid day'

Use a switch statement on dayNumber with cases for numbers 1 to 7

Print the day name corresponding to the number (1 = Monday, 2 = Tuesday, ..., 7 = Sunday)

Print defaultDay if the number is not between 1 and 7

💡 Why This Matters

🌍 Real World

Switch statements are useful when you want to choose between many options based on a single value, like menu choices or day names.

💼 Career

Understanding switch statements helps in writing clear and efficient code for decision-making in many programming jobs.

1

Create the day number variable

Create a variable called dayNumber and set it to 3.

PHP

<?php

// Create a variable called dayNumber and set it to 3
// Your code here

Hint

Use $dayNumber = 3; to create the variable.

2

Create the default day variable

Create a variable called defaultDay and set it to the string 'Invalid day'.

PHP

<?php
$dayNumber = 3;

// Create a variable called defaultDay and set it to 'Invalid day'
// Your code here

Hint

Use $defaultDay = 'Invalid day'; to create the variable.

3

Write the switch statement

Write a switch statement using $dayNumber to set a variable $dayName to the correct day name for numbers 1 to 7: 1 = Monday, 2 = Tuesday, 3 = Wednesday, 4 = Thursday, 5 = Friday, 6 = Saturday, 7 = Sunday. Use $defaultDay for any other number.

PHP

<?php
$dayNumber = 3;
$defaultDay = 'Invalid day';

// Use a switch statement on $dayNumber to set $dayName
// Your code here

Hint

Use switch ($dayNumber) { case 1: ... break; ... default: ... } to assign $dayName.

4

Print the day name

Print the value of the variable $dayName.

PHP

<?php
$dayNumber = 3;
$defaultDay = 'Invalid day';

switch ($dayNumber) {
    case 1:
        $dayName = 'Monday';
        break;
    case 2:
        $dayName = 'Tuesday';
        break;
    case 3:
        $dayName = 'Wednesday';
        break;
    case 4:
        $dayName = 'Thursday';
        break;
    case 5:
        $dayName = 'Friday';
        break;
    case 6:
        $dayName = 'Saturday';
        break;
    case 7:
        $dayName = 'Sunday';
        break;
    default:
        $dayName = $defaultDay;
        break;
}

// Print the day name
// Your code here

Hint

Use print($dayName); to show the day.

Practice

1. What does a switch statement do in PHP?

easy

A. It chooses which code to run based on a value.

B. It repeats code multiple times.

C. It defines a function.

D. It creates a new variable.

Solution

1. Step 1: Understand the purpose of switch

   A switch statement compares a value to multiple cases to decide which code block to run.

2. Step 2: Compare with other options

   Repeating code is done by loops, functions define reusable code, and variables store data, so these are not correct.

3. Final Answer:

   It chooses which code to run based on a value. -> Option A

4. Quick Check:

   Switch selects code by value = A [OK]

Hint: Switch picks code by matching value quickly [OK]

Common Mistakes:

• Confusing switch with loops
• Thinking switch defines functions
• Believing switch creates variables

2. Which of the following is the correct syntax to start a switch statement in PHP?

easy

A. switch [variable] {

B. switch variable {

C. switch (variable) {

D. switch variable() {

Solution

1. Step 1: Recall switch syntax

   In PHP, switch requires parentheses around the variable: switch (variable) {

2. Step 2: Check other options

   Options without parentheses or with brackets or parentheses after variable name are invalid syntax.

3. Final Answer:

   switch (variable) { -> Option C

4. Quick Check:

   Switch uses parentheses around variable [OK]

Hint: Switch always uses parentheses around the variable [OK]

Common Mistakes:

• Omitting parentheses
• Using square brackets instead of parentheses
• Adding parentheses after variable name

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

 $color = 'red';
 switch ($color) {
   case 'blue':
     echo 'Blue color';
     break;
   case 'red':
     echo 'Red color';
     break;
   default:
     echo 'No color';
 }

medium

A. Blue color

B. Syntax error

C. No color

D. Red color

Solution

1. Step 1: Check the value of $color

   $color is set to 'red'.

2. Step 2: Match cases in switch

   The switch checks 'blue' first (no match), then 'red' (match), so it runs echo 'Red color' and breaks.

3. Final Answer:

   Red color -> Option D

4. Quick Check:

   Value 'red' matches case 'red' [OK]

Hint: Match value to case, break stops further checks [OK]

Common Mistakes:

• Forgetting break causes fall-through
• Assuming default runs even if case matches
• Mixing case values

4. Identify the error in this PHP switch code:

 $day = 3;
 switch ($day) {
   case 1:
     echo 'Monday';
   case 2:
     echo 'Tuesday';
     break;
   default:
     echo 'Other day';
 }

medium

A. Missing break after case 1 causes fall-through.

B. Switch statement syntax is incorrect.

C. Variable $day is not defined.

D. Default case should be first.

Solution

1. Step 1: Check breaks in cases

   Case 1 has no break, so if matched, it falls through to case 2.

2. Step 2: Understand effect of missing break

   Missing break causes code for case 2 to run even if case 1 matches, which is usually unintended.

3. Final Answer:

   Missing break after case 1 causes fall-through. -> Option A

4. Quick Check:

   Break missing after case 1 causes fall-through [OK]

Hint: Always add break after each case to avoid fall-through [OK]

Common Mistakes:

• Ignoring missing break causes multiple cases to run
• Thinking default must be first
• Assuming variable is undefined

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

 $score = 85;
 switch (true) {
   case ($score >= 90):
     echo 'Grade A';
     break;
   case ($score >= 80):
     echo 'Grade B';
     break;
   case ($score >= 70):
     echo 'Grade C';
     break;
   default:
     echo 'Fail';
 }

hard

A. Grade A

B. Grade B

C. Grade C

D. Fail

Solution

1. Step 1: Understand switch(true) usage

   The switch compares true to each case condition result.

2. Step 2: Evaluate each case condition

   $score is 85, so ($score >= 90) is false, ($score >= 80) is true, so it matches case 2 and prints 'Grade B'.

3. Final Answer:

   Grade B -> Option B

4. Quick Check:

   Switch(true) matches first true case = Grade B [OK]

Hint: Use switch(true) to check conditions in order [OK]

Common Mistakes:

• Expecting switch to compare values directly
• Not understanding switch(true) trick
• Missing break causing fall-through