Write a programm to print prime number between given numbers in php

class Test

{
    private $returnVar;
    function primeNumber($number) {
        $k = 0;
        //2.3.5.7,11,13,17
        if($number == 0 || $number == 1)
            $this->returnVar = 'Please enter number greater than 1';
        else {
            for($i=2;$i<$number;$i++){
                for($j=2;$j<$i;$j++) {
                    if($i%$j == 0) {
                        $k++;
                    }
                }
                if($k == 0) {
                    $this->returnVar[] = $i;
                }
                $k = 0;
            }
        }
        return $this->returnVar;
    }
}

$testObj = new Test();

$prime = $testObj->primeNumber(20);
print_r($prime);