Assignment and compound assignment in PHP - Mini Project: Build & Apply

Assignment and Compound Assignment in PHP

📖 Scenario: You are managing a small online store's inventory. You need to keep track of the number of items in stock and update the stock as sales happen.

🎯 Goal: Build a simple PHP script that uses assignment and compound assignment operators to update the stock count of a product.

📋 What You'll Learn

Create a variable to hold the initial stock count.

Create a variable to hold the number of items sold.

Use a compound assignment operator to update the stock count after sales.

Print the updated stock count.

💡 Why This Matters

🌍 Real World

Managing inventory counts in an online store or any business that tracks stock.

💼 Career

Understanding assignment and compound assignment is essential for updating values efficiently in programming tasks such as inventory management, financial calculations, and data processing.

1

Create the initial stock count variable

Create a variable called $stock and set it to 50 to represent the initial number of items in stock.

PHP

<?php

// Create a variable called $stock and set it to 50
// Your code here

Hint

Use the assignment operator = to set the value.

2

Create the items sold variable

Create a variable called $sold and set it to 13 to represent the number of items sold.

PHP

<?php

$stock = 50;

// Create a variable called $sold and set it to 13
// Your code here

Hint

Remember to use the assignment operator =.

3

Update the stock using compound assignment

Use the compound assignment operator -= with the variable $stock and the variable $sold to subtract the sold items from the stock.

PHP

<?php

$stock = 50;
$sold = 13;

// Use compound assignment to subtract $sold from $stock
// Your code here

Hint

The -= operator subtracts the right value from the left variable and assigns the result back to the left variable.

4

Print the updated stock count

Write a print statement to display the updated value of $stock.

PHP

<?php

$stock = 50;
$sold = 13;
$stock -= $sold;

// Print the updated stock count
// Your code here

Hint

Use print($stock); to show the current stock.

Practice

1. What does the += operator do in PHP?

easy

A. Assigns the right value to the left variable without any operation

B. Multiplies the left variable by the right value

C. Subtracts the right value from the left variable

D. Adds the right value to the left variable and assigns the result to the left variable

Solution

1. Step 1: Understand the += operator

   The += operator adds the value on the right to the variable on the left.

2. Step 2: Assign the result back to the left variable

   It updates the left variable with the new sum.

3. Final Answer:

   Adds the right value to the left variable and assigns the result to the left variable -> Option D

4. Quick Check:

   += means add and assign [OK]

Hint: Think: add right to left and save in left [OK]

Common Mistakes:

• Confusing += with simple assignment =
• Thinking it subtracts or multiplies
• Believing it only adds without assignment

2. Which of the following is the correct syntax to multiply a variable $x by 5 and update it in PHP?

easy

A. $x *= 5;

B. $x =* 5;

C. $x = *5;

D. $x = 5*;

Solution

1. Step 1: Identify the correct compound assignment syntax

   The correct syntax for multiplying and assigning is $x *= 5; with no spaces between * and =.

2. Step 2: Check other options for syntax errors

   The other options have incorrect placement of operators or missing operands.

3. Final Answer:

   $x *= 5; -> Option A

4. Quick Check:

   Use *= for multiply and assign [OK]

Hint: Remember no space: variable *= value [OK]

Common Mistakes:

• Writing =* instead of *= operator
• Adding spaces between * and =
• Placing * or = incorrectly

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

$a = 10;
$a += 5;
$a -= 3;
echo $a;

medium

A. 10

B. 12

C. 8

D. 15

Solution

1. Step 1: Calculate after first operation

   Initially, $a = 10. After $a += 5;, $a becomes 10 + 5 = 15.

2. Step 2: Calculate after second operation

   Then $a -= 3; subtracts 3: 15 - 3 = 12.

3. Final Answer:

   12 -> Option B

4. Quick Check:

   10 + 5 - 3 = 12 [OK]

Hint: Perform operations step-by-step from top to bottom [OK]

Common Mistakes:

• Ignoring the order of operations
• Adding instead of subtracting in second step
• Confusing initial value with final

4. Identify the error in the following PHP code:

$count = 5;
$count +== 3;
echo $count;

medium

A. Variable name is invalid

B. Missing semicolon after first line

C. Using +== instead of +=

D. echo statement syntax error

Solution

1. Step 1: Check the compound assignment operator

   The operator +== is invalid in PHP. The correct operator to add and assign is +=.

2. Step 2: Verify other parts of code

   Semicolons are present, variable name is valid, and echo syntax is correct.

3. Final Answer:

   Using +== instead of += -> Option C

4. Quick Check:

   Compound assignment must be +=, not +== [OK]

Hint: Remember compound operators have one = only [OK]

Common Mistakes:

• Typing two equal signs in compound assignment
• Confusing comparison (==) with assignment (=)
• Assuming +== is valid operator

5. Given the code below, what will be the value of $result after execution?

$x = 4;
$y = 3;
$result = 10;
$result += $x * $y;
$result -= 5;
$result /= 2;

hard

A. 8.5

B. 6.5

C. 10

D. 9

Solution

1. Step 1: Calculate multiplication and addition

   $x * $y = 4 * 3 = 12. Then $result += 12 means 10 + 12 = 22.

2. Step 2: Subtract 5 from $result

   22 - 5 = 17.

3. Step 3: Divide $result by 2

   17 / 2 = 8.5.

4. Step 4: Check options carefully

   8.5 is 8.5, but note the question asks for final value of $result after all operations.

5. Final Answer:

   8.5 -> Option A

6. Quick Check:

   (10 + 4*3 - 5) / 2 = 8.5 [OK]

Hint: Follow order: multiply, add, subtract, divide [OK]

Common Mistakes:

• Ignoring operator precedence
• Doing operations in wrong order
• Dividing before subtracting