What is the concept of integer overflow in PHP and how does it affect calculations?

Integer overflow in PHP occurs when a mathematical operation results in a value that exceeds the maximum allowable integer value for the data type being used. This can lead to unexpected behavior or errors in calculations. To prevent integer overflow, you can use the `bcmath` extension in PHP, which allows for arbitrary precision arithmetic.

// Using bcmath extension to prevent integer overflow
$num1 = '9223372036854775807'; // Max value for 64-bit signed integer
$num2 = '1';
$result = bcadd($num1, $num2);

echo $result; // Output: 9223372036854775808