PHP

CHARACTER STRINGS IN PHP

Character strings are a series of character sequences, can be combinations of numbers, punctuation characters and letters, words or sentences. The following are some examples of character strings:

$string1="gunston500";
$string2="Hello";
$string3="My name iS John Smith";
$string4='john@smith.com';

When only numbers are stored in variables, no single or double quotes are used so that these variables can be used in mathematical calculations as in the following example:

$firstNumber=156; // number
$secondNumber=44; // number
$totNumber= $firstNumber + $secondNumber; // number

When only numbers are enclosed in single or double quotes, they become character strings and cannot be used in mathematical calculations as in the following example:

$firstNumber="156"; // character string
$secondNumber='44'; // character string

You can use either single or double quotes to store Character strings in a variable but there are differences in the way PHP treats them.

Single-quoted string values are stored literally ie. as is.

Example:

$name="John";

$string='My name is $name'; // stored as: My name is $name

A \ (back slash) is used to escape an apostrophe (') in single quoted strings as the example below:

$string='My mother\'s name is $name'; // stored as: My mother's name is $name

Double-quoted string values are processed before the string is stored.

Example:

$name="John";

$string='My name is $name'; // stored as: My name is John
// ie. the $name variable is evaluated to John and then stored as: My name is John

Using Secial Characters In Double Quoted Strings

Newline \n: Characters proceeding \n start on a new line. Example:

$string="John \nSmith";
echo $string;

The above outputs:

John
Smith

Other special characters:

Carriage-return character: \r
Tab character: \t