Variables
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 42.1 into a new file called ubuntu1.php.
LISTING 42.1 Testing Types in PHP
<?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:
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