'substr' => array('substr', 'substr', gT('Return part of a string'), 'string substr(string, start [, length])', 'https://www.php.net/manual/en/function.substr.php', 2,3),

// Each allowed function is a mapping from local name to external name + number of arguments
        // Functions can have a list of serveral allowable #s of arguments.
        // If the value is -1, the function must have a least one argument but can have an unlimited number of them
        // -2 means that at least one argument is required.  -3 means at least two arguments are required, etc.