Integer type and behavior in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an integer in PHP?

An integer in PHP is a whole number without a decimal point. It can be positive, negative, or zero.

intermediate

What happens when an integer exceeds the platform's maximum size in PHP?

When an integer exceeds the platform's maximum size, PHP converts it to a float (floating-point number) automatically.

beginner

How can you check if a variable is an integer in PHP?

You can use the function is_int() or is_integer() to check if a variable is an integer.

intermediate

What is the size of an integer on a 64-bit PHP platform?

On a 64-bit platform, integers can typically hold values from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.

beginner

Can integers in PHP be written in different number bases? Give examples.

Yes, integers can be written in decimal (e.g., 42), octal (e.g., 052), hexadecimal (e.g., 0x2A), and binary (e.g., 0b101010).

Which function checks if a variable is an integer in PHP?

A is_int()

B is_string()

C is_float()

D is_array()

The function is_int() returns true if the variable is an integer.

What happens if an integer value exceeds PHP's maximum integer size?

A It stays as integer with wrong value

B It throws an error

C It resets to zero

D It becomes a float

PHP automatically converts integers that exceed the max size to floats.

Which of these is a valid hexadecimal integer in PHP?

A 0x1A

B 0b1010

C 052

D 42

0x1A is a hexadecimal integer; 0b1010 is binary, 052 is octal, and 42 is decimal.

On a 64-bit system, what is the approximate maximum integer value PHP can hold?

A 2^31 - 1

B 2^63 - 1

C 2^16 - 1

D 2^8 - 1

On 64-bit systems, PHP integers can hold values up to 2^63 - 1.

Which of these is NOT a valid way to write an integer in PHP?

A 0b1101

B 0xFF

C 08

D 123

08 is invalid because numbers starting with 0 are octal, and 8 is not a valid octal digit.

Explain how PHP handles integers that are too large for the platform's integer size.

Think about what PHP does when numbers get too big.

Describe the different number bases you can use to write integers in PHP and give an example for each.

Remember the prefixes for each base.

Practice

1. Which of the following is a valid integer value in PHP?

easy

A. 42

B. 3.14

C. "100"

D. true

Solution

1. Step 1: Understand integer definition in PHP

   Integers are whole numbers without decimals, like 42 or -7.

2. Step 2: Check each option

   42 is 42, a whole number. 3.14 is 3.14, a float. "100" is a string. true is a boolean.

3. Final Answer:

   42 -> Option A

4. Quick Check:

   Integer = 42 [OK]

Hint: Integers have no decimal point or quotes [OK]

Common Mistakes:

• Confusing strings with integers
• Thinking floats are integers
• Using booleans as integers

2. Which of the following is the correct way to declare an integer variable in PHP?

easy

A. $num = 10;

B. $num = '10';

C. $num = 10.0;

D. $num = true;

Solution

1. Step 1: Identify integer assignment syntax

   In PHP, integers are assigned without quotes and without decimal points.

2. Step 2: Evaluate each option

   $num = '10'; assigns a string '10'. $num = 10; assigns integer 10 correctly. $num = 10.0; assigns a float 10.0. $num = true; assigns a boolean true.

3. Final Answer:

   $num = 10; -> Option A

4. Quick Check:

   Integer assignment = $num = 10; [OK]

Hint: No quotes or decimals for integers [OK]

Common Mistakes:

• Using quotes around numbers
• Assigning floats instead of integers
• Confusing booleans with integers

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

$a = 5;
$b = 2;
$c = $a / $b;
echo (int)$c;

medium

A. 2.5

B. 3

C. Error

D. 2

Solution

1. Step 1: Calculate division result

   $a / $b = 5 / 2 = 2.5 (float)

2. Step 2: Cast float to integer

   (int)2.5 converts to 2 by dropping decimal part.

3. Final Answer:

   2 -> Option D

4. Quick Check:

   Integer cast truncates decimals = 2 [OK]

Hint: Casting float to int drops decimals [OK]

Common Mistakes:

• Expecting rounding instead of truncation
• Confusing output with float value
• Thinking casting causes error

4. Identify the error in this PHP code snippet:

$num = 0123;
echo $num;

medium

A. Outputs 123 as decimal

B. Outputs 83 because of octal interpretation

C. Syntax error due to leading zero

D. Runtime error

Solution

1. Step 1: Understand leading zero in integer literals

   In PHP, numbers starting with 0 are octal (base 8) numbers.

2. Step 2: Convert octal 0123 to decimal

   Octal 123 = 1*64 + 2*8 + 3 = 64 + 16 + 3 = 83 decimal.

3. Final Answer:

   Outputs 83 because of octal interpretation -> Option B

4. Quick Check:

   Leading zero means octal = 83 [OK]

Hint: Leading zero means octal number in PHP [OK]

Common Mistakes:

• Assuming leading zero is ignored
• Expecting decimal output 123
• Thinking it causes syntax error

5. You want to store a large integer value beyond PHP's 32-bit limit. Which approach correctly handles this in PHP?

hard

A. Use a float type to store the large number

B. Use an array to split the number into parts

C. Use a string to store the number and perform math with BCMath functions

D. Use an integer variable; PHP automatically supports large integers

Solution

1. Step 1: Recognize PHP integer size limits

   PHP integers have size limits (32-bit or 64-bit depending on system). Large numbers can overflow.

2. Step 2: Choose correct method for large integers

   Using strings with BCMath functions allows precise math on large numbers beyond integer limits.

3. Final Answer:

   Use a string to store the number and perform math with BCMath functions -> Option C

4. Quick Check:

   Large integer math needs strings + BCMath [OK]

Hint: Use strings + BCMath for big integers [OK]

Common Mistakes:

• Using floats causes precision loss
• Assuming PHP integers auto-expand
• Trying to split number manually in arrays