public static String bcpowmod(Environment env, Memory _base, Memory _exp, Memory _modulus){
        return bcpowmod(env, _base, _exp, _modulus, getScale(env));
    }
bcmath extension
http://www.php.net/manual/ru/book.bc.php
exts/jphp-zend-ext/src/main/java/org/develnext/jphp/zend/ext/standard/BCMathFunctions.java