string - Compare variables PHP

Question

How can I compare two variable strings, would it be like so:

$myVar = "hello";
if ($myVar == "hello") {
//do code
}

And to check to see if a $_GET[] variable is present in the url would it be like this"

$myVars = $_GET['param'];
if ($myVars == NULL) {
//do code
}

Answer 1

$myVar = "hello";
if ($myVar == "hello") {
    //do code
}

$myVar = $_GET['param'];
if (isset($myVar)) {
    //IF THE VARIABLE IS SET do code
}


if (!isset($myVar)) {
    //IF THE VARIABLE IS NOT SET do code
}

For your reference, something that stomped me for days when first starting PHP:

$_GET["var1"] // these are set from the header location so www.site.com/?var1=something
$_POST["var1"] //these are sent by forms from other pages to the php page