PHP HereDoc 引用系统常量、自定义常量、类和对象中常量与静态变量

定义常量

//define public const
define("TEST_DEFINDE_CONST_NAME","test define const var value");

类常量及静态变量

//define class const and static var
class TestClass
{
    public const TEST_CLASS_CONST_NAME = "test class const var value";
    public static $test_class_static_var = "test class static var value";
    function  __construct()
    {
    }
}

定义 `HEREDOC` 中引用函数（也可定义为全局函数和变量）

class TestPublic
{
    public static function heredocGetConst($string): string
    {
        return $string;
    }
    //define const HGC
    //public const HGC = __CLASS__ . '::' . 'heredocGetConst';
    //define static function HGC
    public static function HGC(){
        static $HGC = null;
        if(is_callable([__CLASS__ , "heredocGetConst"],callable_name:$HGC)){
            return $HGC;
        }
    }
}

在 `HEREDOC` 中引用

class TestHeredocOutConst
{
    public static function testHeredocOutConst(){
        //$HGC = TestPublic::HGC;
        $HGC = TestPublic::HGC();
        $testClass = new TestClass();
        $test_heredoc = <<<HEREDOC
            test HereDoc output const :
                define const(TEST_DEFINDE_CONST_NAME)                : {$HGC(TEST_DEFINDE_CONST_NAME)}
                class const(TestClass::TEST_CLASS_CONST_NAME)        : {$HGC(TestClass::TEST_CLASS_CONST_NAME)}
                class static var (TestClass::\$TEST_CLASS_CONST_NAME) : {$HGC(TestClass::$test_class_static_var)}
                object const(TestClass::TEST_CLASS_CONST_NAME)       : {$HGC($testClass::TEST_CLASS_CONST_NAME)}
                object const(TestClass::\$test_class_static_var)      : {$HGC($testClass::$test_class_static_var)}
                system const(PHP_PREFIX)                             : {$HGC(PHP_PREFIX)};
            ok!{$HGC(PHP_EOL)}
            HEREDOC;
        return $test_heredoc;
    }
}
echo TestHeredocOutConst::testHeredocOutConst();

测试输出 `output`

test HereDoc output const :
    define const(TEST_DEFINDE_CONST_NAME)                : test define const var value
    class const(TestClass::TEST_CLASS_CONST_NAME)        : test class const var value
    class static var (TestClass::$TEST_CLASS_CONST_NAME) : test class static var value
    object const(TestClass::TEST_CLASS_CONST_NAME)       : test class const var value
    object const(TestClass::$test_class_static_var)      : test class static var value
    system const(PHP_PREFIX)                             : /usr/local/php8;
ok!