This gist is about how to test for class constants defined inside a class from within the class or outside the class

testStaticVariable.php

<?php
/**
 * THIS GIST IS ABOUT HOW TO TEST FOR CLASS CONSTANTS IN PHP INSIDE AND OUTSIDE THE CLASS
 * @author Adebola Samuel Olowofela <samcrosoft@gmail.com>
 * @link https://github.com/samcrosoft
 * @class SampleClass
 */

class SampleClass
{
    const CONST1 = 1;

    const CONST2 = "two";

    const CONST3 = "three";


    /**
     * This method returns a class constant if it exists
     * @param string $sConstantName
     * @return mixed|null
     */
    public function getClassConstantVariable($sConstantName = "")
    {
        if($this->testIfClassConstantExists($sConstantName) === true)
        {
            // note : you can use self:: instead of static::
            return constant("static::$sConstantName");
        }
        else
        {
            // note you can decide to throw an error here and return false or any other value
            // i have decided to return null
            return null;
        }
    }

    /**
     * This method tests if a class constant exists or not
     * @param string $sConstantName
     * @return bool
     */
    private function testIfClassConstantExists($sConstantName = "")
    {
        $bExists = false;

        if(!empty($sConstantName) && is_string($sConstantName))
        {
            // note : you can use self:: instead of static::
            $bExists = defined("static::$sConstantName") ? true : false;
        }

        return $bExists;
    }

}



// IDEA 1: TESTING FOR A CLASS CONSTANT OUTSIDE THE CLASS
//to test if the class "SampleClass" has a class constant declared or not


if(defined('SampleClass::CONST1'))
{
    //defined
    // perform action for defined
}
else
{
    //not defined
    // perform not defined action
}


// IDEA 2 : Using Object Oriented Approach
// TESTING USING THE OBJECT ORIENTED APPROACH
// testing using the sample class
$oSampleClass = new SampleClass();
print $oSampleClass->getClassConstantVariable("CONST1"). "\n";        // should print 1
print $oSampleClass->getClassConstantVariable("CONST2"). "\n";        // should print two
var_dump($oSampleClass->getClassConstantVariable("CONST10"));          // should display null