Learning PHP, MySQL, JavaScript, and CSS, 2nd Edition

Implicit and Explicit Casting

PHP is a loosely typed language that allows you to declare a variable and its type simply by using it. It also automatically converts values from one type to another whenever required. This is called implicit casting.

However, there may be times when PHP’s implicit casting is not what you want. In Example 4-37, note that the inputs to the division are integers. By default, PHP converts the output to floating-point so it can give the most precise value—4.66 recurring.

Example 4-37. This expression returns a floating-point number

<?php
$a = 56;
$b = 12;
$c = $a / $b;
echo $c;
?>

But what if we had wanted $c to be an integer instead? There are various ways in which this could be achieved. One way is to force the result of $a / $b to be cast to an integer value using the integer cast type (int), like this:

$c = (int) ($a / $b);

This is called explicit casting. Note that in order to ensure that the value of the entire expression is cast to an integer, the expression is placed within parentheses. Otherwise, only the variable $a would have been cast to an integer—a pointless exercise, as the division by $b would still have returned a floating-point number.

You can explicitly cast to the types shown in Table 4-6, but you can usually avoid having to use a cast by calling one of PHP’s built-in functions. For example, to obtain an integer value, you could use the intval function. As with some other sections in this book, this one is mainly here to help you understand ...