解释器模式

/**
  interpreter模式
*/
class Expression
{
    function interpreter($str)
    {
        return$str;
    }
}

class ExpressionNum extends Expression
{
    function interpreter($str)
    {
        switch ($str) {
            case"0":return"零";
            case"1":return"一";
            case"2":return"二";
            case"3":return"三";
            case"4":return"四";
            case"5":return"五";
            case"6":return"六";
            case"7":return"七";
            case"8":return"八";
            case"9":return"九";
        }
    }
}

class ExpressionCharater extends Expression
{
    function interpreter($str)
    {
        return strtoupper($str);
    }
}

class Interpreter
{
    function execute($string)
    {
        $expression = null;
        for ($i= 0;$i<strlen($string);$i++) {
            $temp = $string[$i];
            $expression = is_numeric($temp) ? new ExpressionNum() : new ExpressionCharater();
            echo$expression->interpreter($temp);
        }
    }
}

$obj=new Interpreter();
$obj->execute("12345abc");

参考文章 https://wenku.baidu.com/view/b4c78b4702768e9951e738fb.html