使用PHP中的变量访问const [duplicate]

Question

This question already has an answer here:

• Dynamic constant name in PHP 3 answers

Let me explain with a real example:

class Config{
 const DB_NAME = "FOO";
}

class ConfigLoader{
 public static function get($key) {
   return Config::$key;
 }
 public static function getTest() {
   return Config::DB_NAME;
 }
}

ConfigLoader::get("DB_NAME"); // return error: Access to undeclared static property

ConfigLoader::getTest(); // It's OK! return FOO

But i need to do something like ConfigLoader::get("DB_NAME) method

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Answer 1

I ain't found a direct way to access constants of class. But by using reflection class it's possible.

class ConfigLoader
{
    public static function get($key)
    {
        return (new ReflectionClass('Config'))->getConstant('DB_NAME');
        // return (new ReflectionClass('Config'))->getConstants()['DB_NAME'];
    }

    public static function getTest()
    {
        return Config::DB_NAME;
    }
}


echo ConfigLoader::get('DB_NAME'); // return error: Access to undeclared static property

The ReflectionClass class reports information about a class.
ReflectionClass::getConstant — Gets defined constant
ReflectionClass::getConstants — Gets constants

Output

FOO

Demo.