A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).
Rules for PHP variables:
A variable starts with the $ sign, followed by the name of the variable
A variable name must start with a letter or the underscore character
A variable name cannot start with a number
A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
Variable names are case-sensitive ($age and $AGE are two different variables)
<?php
$txt = "Hello world!";
$x = 5;
$y = 10.5;
?>
After the execution of the statements above, the variable $txt will hold the value Hello world!, the variable $x will hold the value 5, and the variable $y will hold the value 10.5.
Note: When you assign a text value to a variable, put quotes around the value.
Note: Unlike other programming languages, PHP has no command for declaring a variable. It is created the moment you first assign a value to it.
The PHP echo statement is often used to output data to the screen.
The following example will show how to output text and a variable:
<?php
$txt = "thoengwit.ac.th";
echo "I love $txt!";
?>
The following example will produce the same output as the example above:
<?php
$txt = "thoengwit.ac.th";
echo "I love " . $txt . "!";
?>
The following example will output the sum of two variables:
<?php
$x = 5;
$y = 4;
echo $x + $y;
?>
Create a variable named txt and assign the value "Hello".
Create one variable named x, and one variable named y, then use the echo statement to output the sum of x and y.
Create a variable named stdname and assign the value "Yotin Siriaey".
Create a variable named myold and assign the value 35.
Create a variable named num1 and assign the value 5.56