How can you access class constants in PHP using a variable-stored name?

Accessing Class Constants with Variable-Stored Names

In object-oriented programming, class constants provide a convenient way to define immutable values within a class. However, accessing these constants using a variable that contains their names poses a challenge.

Consider the following example:

<code class="php">class A {
    const MY_CONST = "value";
}

$myVar = "MY_CONST";</code>

In this scenario, attempting to access the value of MY_CONST using self::$myVar won't work because it refers to a static property rather than a constant.

Fortunately, there are two methods to bypass this limitation:

Constant Function:

The constant function enables access to constants defined via both define and class declarations. It takes the form constant('::'), where :: represents the namespace and constName specifies the constant's name.

<code class="php">$c = 'MY_CONST';
echo constant('::' . $c); // Output: value</code>

Reflection Class:

Using the Reflection API, one can access class constants through a reflection class instance.

<code class="php">$ref = new ReflectionClass('A');
$constName = 'MY_CONST';
echo $ref->getConstant($constName); // Output: value</code>

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