Way to write php script

At first need to a notpad or html file then change the extension .php. Then it will be php file. Then we are ready to work with php script or coding.
At first show to php script starting
<?php -- strating

All kind of text and code or script here.

?> -- ending

We see a example,

<?php
<h1>Softandweb</h1>
echo "Hello world"
?>

we see browser through local host :
 Then we will see browsers like

Softandweb

Hello world