How can I use the value of a variable as constant?

Question

1. I have a PHP site which uses language system based on "define" method. For example:

    define("_question_1", "How old are you?"); define("_question_2", "Question 2?"); define("_question_3", "Question 3?"); .... define("_question_10", "Question 10?"); 

2. I have 5-10 questions I need to ask. And I need to select what question I want to ask. So I make a query to my DB. Something like:

    SELECT q_title FROM questions_db WHERE id=3 OR id=10; 

   Database returns two TEXT(!) values:

    _question_3, _question_10 

   Which I save to:

    $a = _question_3; $b = _question_10; 

3. Next thing I need is to show the text of the description defined earlier. When I use _question_3 as VARIABLE it works like this:

    echo ""._question_3.""; //returns "Question 3?" 

   But I have only _question_3 as TEXT value and it's works like this:

    echo "".$a.""; //returns "_question_3" 

THE QUESTION: How to convert text value to PHP variable and make something like?

    define("_question_3", "Question 3?");
    $a = _question_3; //text value
    //do something with $a.... 
    echo "".$a.""; //returns "Question 3?"

Thanks for help. PS Please change the title if it doesn't clear to understanding.

Answer 1

只需使用constant()即可将变量值用作常量，例如

echo constant($a);

Answer 2

1. In PHP you could use variable variable – dynamic variable names.

    $a = '_question_3'; $b = 'Question 3?'; $$a = $b; echo $b; // prints "Question 3?" echo $_question_3; // prints "Question 3?" 

But it's not good solution. Try not to use dynamic variable names.

2. May be associative array will be more suitable to you?

    $questions = []; // Creating an empty array $questions['_question_3']['question'] = 'Question 3?'; // Storing a question $questions['_question_3']['answers'] = [ // Adding answers 'Answer 1', 'Answer 2', 'Answer 3' ]; 

3. Or declare a Question class and create instances of it.

    class Question { public $Question; public $Answers; __construct($question, $answers) { $this->Question = $question; $this->Answers = $answers; } } $q1 = new Question('Question 1?', ['Answer 1', 'Answer 2', 'Answer 3']); 

Answer 3

Try constant() it returns the value of a constant, for example:

var_dump(constant('YourConstantNameHere'));

or with variables

var_dump(constant($a));

http://www.php.net/manual/en/function.constant.php