Here we will learn about the filter functions that are used to validate and sanitize the data and make sure that data is in proper form and all the illegal characters are removed from the data.The filter function are:
filter_has_var()
filter_id()

The filter_has_var() helps us to find the variable is of same input type as it was specified.We can check for any type of variable.

Syntax: filter_has_var(type, variable)

type can be as follows: INPUT_GET
INPUT_POST
INPUT_COOKIE
INPUT_SERVER
INPUT_ENV

For Example:

<?php
if (!filter_has_var(INPUT_GET, "email")) {
    echo("No Email Exists");
} else {
    echo("Email Exists");
}
?> 

filter_id() function returns the filter ID of the VALIDATE_IP / Stripped filter:

For Example:

<?php
$echo(filter_id("validate_ip")); 
$echo(filter_id("stripped"));
?>
output: 275
output:513