Integer type and behavior in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code?

Consider the following PHP code snippet. What will it output?

PHP

<?php
$a = PHP_INT_MAX;
$b = $a + 1;
echo gettype($b);
?>

A "double"

B "integer"

C "string"

D "boolean"

💡 Hint

Think about what happens when you add 1 to the largest integer PHP can hold.

Adding 1 to PHP_INT_MAX causes integer overflow, so PHP converts the value to a float (double).

❓ Predict Output

intermediate

What is the value of $result after this code runs?

What will be the value of $result after executing this PHP code?

PHP

<?php
$result = (int) "123abc" + 10;
echo $result;
?>

A 133

B 10

C 123abc10

D 0

💡 Hint

How does PHP convert a string to an integer when the string starts with digits?

PHP converts the initial numeric part of the string to integer, ignoring the rest. So "123abc" becomes 123, plus 10 equals 133.

🔧 Debug

advanced

What error does this PHP code raise?

What error or output will this PHP code produce?

PHP

<?php
$val = 1 << 65;
echo $val;
?>

A Fatal error: Unsupported operand types

B 1

C Notice: Bit shift exceeds integer size

D 0

💡 Hint

Consider how PHP handles bit shifts larger than the integer size on 64-bit systems.

In PHP, shifting an integer by more than or equal to the number of bits results in 0. So 1 << 65 outputs 0.

📝 Syntax

advanced

Which option causes a syntax error in PHP?

Which of the following PHP code snippets will cause a syntax error?

A <?php $num = 0123; echo $num; ?>

B <?php $num = 1,000; echo $num; ?>

C <?php $num = 1_000; echo $num; ?>

D <?php $num = 0x1A; echo $num; ?>

💡 Hint

Check how PHP handles numeric literals and commas.

Option B uses a comma inside a number literal, which is invalid syntax in PHP.

🚀 Application

expert

How many items are in the array after this code runs?

Given the following PHP code, how many items does the array $arr contain?

PHP

<?php
$arr = [];
$arr[1] = 'a';
$arr[1.5] = 'b';
$arr[true] = 'c';
$arr[null] = 'd';
$arr['1'] = 'e';
?>

A 3

B 4

C 2

D 1

💡 Hint

Remember how PHP converts array keys to integers.

PHP converts keys to integers or strings. Here, keys 1, 1.5, true, and '1' all become integer 1, overwriting each other. Null becomes empty string key. So keys are 1 and "" resulting in 2 items.

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