Codice PHP:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script language="JavaScript" type="text/JavaScript">
var data0=document.getElementsByTagName('p');
function uno()
{
    data1=document.getElementsByTagName('p');
    var data2=document.getElementsByTagName('p');
}

function due()
{
    alert(data0.length);
    alert(data1.length);
    alert(data2.length);
}
window.onload = function()
{
uno();
due();
}
</script>

</head>

<body>


uno</p>


due</p>


tre</p>
</body>
</html>