The function_argc function returns the number of arguments with which function name is declared. -1 is returned if name is not a known function.

If varname is given, the minimum number of arguments is assigned to that variable. varname must be either a scalar variable or array element.

function_argc works for both built-in functions and those defined in ACL. If name is an ACL function not yet loaded but declared via autoload, function_argc will cause the function to be loaded to return the actual argument counts.