Php-data Types

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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:

$a="World"; echo "Hello\t$a\n";

This displays "Hello" followed by a tab and then "World" followed by a newline. In other words, variable substitution is performed on the variable $a and the escape sequences are converted to their corresponding characters. Contrast that with:

echo 'Hello\t$a\n';

In this case, the output is exactly "Hello\t$a\n". There is no variable substitution or handling of escape sequences.

Another way to assign a string is to use what is known as

Arrays

An array is a compound data type that can contain multiple data values, indexed either numerically or with strings. For example, an array of strings can be written like this:

$var[0]="Hello"; $var[1]="World";

Note that when you assign array elements like this, you do not have to use consecutive numbers to index the elements.

As a shortcut, PHP allows you to add an element onto the end of an array without specifying an index. For example:

$var[ ] ="Test";

PHP picks the next logical numerical index. In this case, the "Test" element is given the index 2 in our $var array: if the array has nonconsecutive elements, PHP selects the index value that is one greater than the current highest index value. This autoindexing feature is most useful when dealing with multiple-choice HTML <select> form elements, as we'll see in a later example.

Posted by Hodie J