$_GET shows empty value
<p>I have a <code>test.php</code> and i have the below code</p>

<pre><code>&lt;?php

    if(isset($_GET['p']) or $_GET['p'] != null) {
        echo $_GET['p'];
    } else {
        echo "Not found";
    }

?&gt;
</code></pre>

<p>I have listed out below urls then required output are show</p>

<pre><code>Test 1 : http://localhost/example/test.php
output : Notice: Undefined index: p in R:\xampp\htdocs\example\test.php on line 3
        Not found


Test 2 : http://localhost/example/test.php?p
output : blank page



Test 3 : http://localhost/example/test.php?p=
output : blank page


Test 4 : http://localhost/example/test.php?p=1
output : 1
</code></pre>

<p>I accept that <code>Test 1</code> and <code>Test 2</code> are <code>true</code>
But when <code>Test 2</code> and <code>Test 3</code> fails out the solution.</p>
