php if (not this or not this) {do some thing}

I try this a lot of time but it not working. I want to do like first one chicking but second one not working. Please Help Me

This code is working.

<?php
    $a = 2;

    if ( $a == 2 || $a == 3 ) {
        echo "OK";
    }else {
        echo "Error !!!!!!!";
    }
?>

but this one not working its all time true.

<?php
    $a = 2;

    if ( $a !== 2 || $a !== 3 ) {
        echo "Error";
    }
?>

Please Help Me