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[Edit] Scalar Data Types
Scalar data types are used to represent a single value. Several data types fall under this category, including Boolean, integer, float, and string.

Boolean

The Boolean datatype is named after George Boole (1815–1864), a mathematician who is considered to be one of the founding fathers of information theory. The Boolean data type represents truth, supporting only two values: TRUE and FALSE (case insensitive). Alternatively, you can use zero to represent FALSE, and any nonzero value to represent TRUE. A few examples follow:
$var = false; // $var is false.
$var = 1; // $var is true.
$var = -1; // $var is true.
$var = 5; // $var is true.
$var = 0; // $var is false.

Integer

An integer is representative of any whole number or, in other words, a number that does not contain fractional parts. PHP supports integer values represented in base 10 (decimal), base 8 (octal), and base 16 (hexadecimal) numbering systems, although it’s likely you’ll only be concerned with the first of those systems. Several examples follow:
42 // decimal
-678900 // decimal
0755 // octal
0xC4E // hexadecimal
The maximum supported integer size is platform-dependent, although this is typically positive or negative 2^31 for PHP version 5 and earlier. PHP 6 introduced a 64-bit integer value, meaning PHP will support integer values up to positive or negative 2^63 in size.

Float

Floating-point numbers, also referred to as floats, doubles, or real numbers, allow you to specify numbers that contain fractional parts. Floats are used to represent monetary values, weights, distances, and a whole host of other representations in which a simple integer value won’t suffice. PHP’s floats can be specified in a variety of ways, several of which are demonstrated here:
4.5678
4.0
8.7e4
1.23E+11

String

Simply put, a string is a sequence of characters treated as a contiguous group. Strings are delimited by single or double quotes The following are all examples of valid strings:
"PHP is a great language"
"123-go"
PHP treats strings in the same fashion as arrays, allowing for specific characters to be accessed via array offset notation. For example, consider the following string:
$color = "maroon";
You could retrieve a particular character of the string by treating the string as an array, like this:
$parser = $color[2]; // Assigns 'r' to $parser
September 16, 2011