Data Types
PHP provides four primitive data types: integers, floating point numbers, strings, and booleans. In addition, there are two compound data types: arrays and objects.
Integers
Integers are whole numbers. The range of
integers in PHP is equivalent to the range of the
long
data type in C. On 32-bit platforms, integer
values range from -2,147,483,648 to +2,147,483,647. PHP automatically
converts larger values to floating point numbers if you happen to
overflow the range. An integer can be expressed in decimal (base-10),
hexadecimal (base-16), or octal (base-8). For example:
$decimal=16; $hex=0x10; $octal=020;
Floating Point Numbers
Floating point numbers represent decimal
values. The range of floating point numbers in PHP is equivalent to
the range of the double
type in C. On most
platforms, a double can be between 1.7E - 308 to 1.7E + 308. A double
may be expressed either as a regular number with a decimal point or
in scientific notation. For example:
$var=0.017; $var=17.0E-3
PHP also has two sets of functions that let you manipulate numbers with arbitrary precision. These two sets are known as the BC and the GMP functions. See http://www.php.net/bc and http://www.php.net/gmp for more information.
Strings
A string is a sequence of characters. A string can be delimited by single quotes or double quotes:
'PHP is cool' "Hello, World!"
Double-quoted strings are subject to variable substitution and escape sequence handling, while single quotes are not. For example:
$a="World"; ...
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