Assignment and compound assignment in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the assignment operator = do in PHP?

It assigns the value on the right side to the variable on the left side. For example, $a = 5; sets the variable $a to 5.

beginner

What is a compound assignment operator?

A compound assignment operator combines an operation with assignment. For example, $a += 3; adds 3 to $a and then assigns the result back to $a.

beginner

List three common compound assignment operators in PHP.

1. += (addition assignment)
2. -= (subtraction assignment)
3. *= (multiplication assignment)

beginner

What happens when you write $x *= 2; if $x is 4?

The value of $x becomes 8 because it multiplies the current value (4) by 2 and assigns the result back to $x.

beginner

Can compound assignment operators be used with strings in PHP? Give an example.

Yes. For example, $str = 'Hello'; $str .= ' World'; appends ' World' to $str, so $str becomes 'Hello World'.

What does $a += 5; do in PHP?

A Assigns 5 to $a

B Adds 5 to $a and assigns the result to $a

C Subtracts 5 from $a

D Multiplies $a by 5

The operator += adds the right value to the left variable and assigns the result back.

Which operator assigns a value to a variable?

A =

B ==

C +=

D !=

The single equals sign = is the assignment operator.

What will be the value of $x after $x = 10; $x -= 3;?

A 3

B 13

C 7

D 10

The -= operator subtracts 3 from 10 and assigns 7 to $x.

Which compound assignment operator appends a string in PHP?

A *=

B -=

C +=

D .=

The .= operator appends the right string to the left string variable.

What does $a *= 4; do if $a is 2?

A Sets $a to 8

B Sets $a to 2

C Sets $a to 4

D Sets $a to 6

It multiplies 2 by 4 and assigns 8 to $a.

Explain how the compound assignment operator += works in PHP with an example.

Think about adding a number to a variable and saving it.

Describe the difference between the assignment operator = and the compound assignment operator *=.

One just sets a value, the other does math then sets.

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