Get class constant names in php?

Question

I have a php class with some class constants that indicate the status of an instance.

When I'm using the class, after I run some methods on it, I do some checks to make sure that the status is what I expect it to be.

For instance, after calling some methods, I expect the status to be MEANINGFUL_STATUS_NAME.

$objInstance->method1();
$objInstance->method2();
if ( $objInstance->status !==  class::MEANINGFUL_STATUS_NAME ) { 
    throw new Exception("Status is wrong, should not be " . class::MEANINGFUL_STATUS_NAME . ".");
}

However, this gives me the exception message

"Status is wrong, should not be 2"

when what I really want to see is

"Status is wrong, should not be MEANINGFUL_STATUS_NAME"

So I've lost the meaningfulness of the constant name. I was thinking of making an 'translation table' array, so I can take the constant values and translate them back into their name, but this seems cumbersome. How should I translate this back, so I get an error message that gives me a better idea of what went wrong?

This is more or less a repeat of http://stackoverflow.com/questions/255312/how-to-get-a-variable-name-as-a-string-in-php — KingRadical, May 18 '10 at 18:49
possible duplicate of [Can I get CONST's defined on a PHP class?](http://stackoverflow.com/questions/956401/can-i-get-consts-defined-on-a-php-class) — outis, Sep 26 '11 at 05:48

score 6 · Answer 1 · answered May 18 '10 at 18:46

This is kind of tricky solution:

$r = new ReflectionClass("YourClassName");
$constantNames = array_flip($r->getConstants());

$objInstance->method1();   
$objInstance->method2();   
if ( $objInstance->status !== YourClassName::MEANINGFUL_STATUS_NAME ) {    
    throw new Exception("Status is wrong, should not be " . $constantNames[YourClassName::MEANINGFUL_STATUS_NAME] . ".");   
}

score 1 · Accepted Answer · answered May 18 '10 at 14:46

1

It occurs to me now that I could use strings as the values for the constants. I'm used to seeing numbers. Is there a reason why I shouldn't do this, or why this wouldn't work?

answered May 18 '10 at 14:46

user151841

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2

You marked your answer as the solution and yet... your answer is a question :) – vectorialpx Apr 28 '16 at 15:07
@vectorialpx I would say rather that this answer prompts a new question/issue, outside the scope of the original. – user151841 Apr 28 '16 at 15:38

score 0 · Answer 3 · edited May 23 '17 at 10:28

Another way might be to let the object check if the status is in a desired mode.

If it is not, the object's method can throw the Exception.

Untested example:

class Klasse
{
    const WANTED_VALUE    =  1;
    const UNWANTED_VALUE  =  2;

    private static $constant_names  =  array();
    p... function __construct ()
    {
        if ( empty( self::$constant_names ) )
        {
            $class            =  new ReflectionClass( __CLASS__ );
            $constants        =  $class->getConstants();
            $constants        =  array_flip( $constants );// requires the constant's values to be unique
            self::$constants  =  $constants;
        }
    }
    public function checkNeededStatus ()
    {
        $needed_status  =  self::WANTED_VALUE;// could also be a parameter(an argument) with a default value
        if ( $this->status !== $needed_status )
        {
            $constant_name  =  self::$constants[ $this->status ];
            $message        =  'Status is wrong, '
                . 'should not be: `' . $constant_name . '`.'
            ;
            //$message .=  '(it should be `' . self::$constants[ $needed_status ] . '`)';
            throw new Exception( $message );
        }
    }
}

$objInstance  =  new Klasse();
$objInstance->method1();
$objInstance->method2();
$objInstance->checkNeededStatus();

credit :

It might be good to consider not using Reflection. Because the thrown message stays inside the class, this has become more likely to do without loosing much maintainability.

Get class constant names in php?

3 Answers3

Untested example:

credit :