All variables in PHP start with a dollar sign (
$). Unlike many other languages, PHP does not have different types of variable for integers, floating-point numbers, arrays, or Booleans. They all start with a
$, and all are interchangeable. As a result, PHP is a weakly typed language, which means you do not declare a variable as containing a specific type of data; you just use it however you want to.
Save the code in Listing 39.1 into a new file called
<?php $i = 10; $j = "10"; $k = "Hello, world"; echo $i + $j; echo $i + $k;?>
To run that script, bring up a console and browse to where you saved it. Then type this command:
matthew@seymour:~$ php ubuntu1.php
If PHP is installed correctly, ...