What is the purpose of the filter_var() function in PHP?

The filter_var() function in PHP is designed specifically to filter a variable using specified filters, making it a valuable tool for sanitizing and validating user input. This function allows developers to apply a variety of predefined filters to a variable, such as stripping tags, validating email addresses, and ensuring that numeric values are within certain ranges. By doing so, it enhances security by helping to prevent common vulnerabilities like cross-site scripting (XSS) or SQL injection.

While the other options touch on useful concepts in PHP, they do not accurately capture the primary role of filter_var(). The function does not inherently convert data types, create filters (though it uses existing ones), or validate database records directly—it is focused on managing filtering and sanitization of individual variables instead.