ZEND PHP 5 Certification STUDY GUIDE

12 ” PHP Basics
ply the names of the data type you want to convert to enclosed in parentheses and
placed before an expression. For example:
$x = 10.88;
echo (int) $x; // Outputs 10
Note that a value cannot be converted to some special types; for example, you cannot
convert any value to a resource—you can, however, convert a resource to a numeric
or string data type, in which case PHP will return the numeric ID of the resource, or
the string Resource id # followed by the resource ID.
Variables
Variables are temporary storage containers. In PHP, a variable can contain any type
of data, such as, for example, strings, integers, floating-point numbers, objects and
arrays. PHP is loosely typed, meaning that it will implicitly change the type of a variable
as needed, depending on the operation being performed on its value. This contrasts
with strongly typed languages, like C and Java, where variables can only contain
one type of data throughout their existence.
PHP variables are identified by a dollar sign $, followed by an identifier name. Variables
must be named using only letters (a-z, A-Z), numbers and the underscore character;
their names must start with either a letter or an underscore, and are one of only
two identifier types in PHP that are case-sensitive (the other is constants, discussed
below). Here are a few examples:
$name = ’valid’; // Valid name
$_name = ’valid’; // Valid name
$1name = ’invalid’; // Invalid name, starts with a number
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Variables can also be interpolated—that is, inserted—directly into certain types of
strings. This is described in the Strings chapter.