(PHP 5 >= 5.2.0, PHP 7)
filter_has_var — Checks if variable of specified type exists
input_type
One of INPUT_GET, INPUT_POST, INPUT_COOKIE, INPUT_SERVER, or INPUT_ENV.
var_name
Name of a variable to check.
Returns true on success or false on failure.
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https://www.php.net/manual/en/function.filter-has-var.php