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.