How to Retrieve Constants Defined in PHP Classes?

Retrieving Constants Defined in PHP Classes

A common task in PHP programming involves obtaining a list of constants defined within specific classes. This information is crucial for accessing and manipulating class-specific constants in a programmatic way.

The challenge lies in finding a suitable method that allows for this retrieval. The native function get_defined_constants() provides a list of all constants in the current scope, but it does not filter for constants defined in a particular class.

The solution to this problem lies in utilizing PHP's Reflection API. This API enables introspection and manipulation of classes and objects at runtime. By leveraging the ReflectionClass object, you can access the class's constants.

Here is the code snippet provided in the question, slightly modified for clarity:

class Profile {
    const LABEL_FIRST_NAME = "First Name";
    const LABEL_LAST_NAME = "Last Name";
    const LABEL_COMPANY_NAME = "Company";
}

$refl = new ReflectionClass('Profile');
$constants = $refl->getConstants();

foreach ($constants as $name => $value) {
    echo "$name: $value\n";
}

This code will iterate through the array of constants and print their names and values. The output will resemble the desired array structure of constant names only.

Note that the Reflection API is comparatively slower than native PHP functions. Therefore, if you anticipate extensive use of this functionality, caching the results for performance optimization is recommended.

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