The first line of this code provides a template for what a customer’s input should look like. Hey Dan, what I did was added and example of how the number should be enter, this is near the input field and will give user the hint as to how they should enter the number. Client-Side Validation: In Client-side validation, Validation will be performed on the client web applications like browsers/any other. PHP Form Validation. Phone Number validation. As of PHP 5.4.11, the numbers +0 and -0 validate as both integers as well as floats (using FILTER_VALIDATE_FLOAT and FILTER_VALIDATE_INT).Before PHP 5.4.11 they only validated as floats (using FILTER_VALIDATE_FLOAT).. Note: . 2.