How can a lack of understanding of PHP data types lead to unexpected results when processing form data?

A lack of understanding of PHP data types can lead to unexpected results when processing form data because PHP is a loosely typed language, meaning it can automatically convert data types. This can result in unintended conversions or comparisons when handling form inputs, leading to errors or incorrect behavior. To avoid this, it's important to explicitly cast form data to the correct data type before using it in any calculations or comparisons.

// Example of explicitly casting form data to the correct data type
$age = (int)$_POST['age'];
$name = (string)$_POST['name'];

// Now $age is an integer and $name is a string, ensuring correct data type usage