programming-for-dummies

Declaring Variables 499
Declaring Variables
PHP variables can hold any type of data, so a variable might hold a string
one moment and a number the next. To declare a variable in PHP, you must
begin every variable name with the dollar symbol ($), such as
Book V
Chapter 4
$VariableName = value;
PHP
VariableName can be any descriptive name, but PHP is a case-sensitive language
so $MyAge is considered a completely different variable from $myage.
Some programmers use uppercase letters to make variable names easier to
find, and others use all lowercase.
One unique feature of PHP is its ability to reference the same value. For
example, consider the following code:
$myage = 35;
$yourage = $myage;
$myage = 109;
In this example, the $myage variable is initially set to 35 and the $yourage
variable is set to the $myage variable, which means the $yourage variable
also contains the value of 35. The third line stores the value 109 into the
$myage variable, but the $yourage variable still holds the value of 35.
By referencing variables with the ampersand symbol (&), PHP allows a variable
to contain identical data without specifically assigning those values. For
example:
$myage = 35;
$yourage = &$myage;
$myage = 109;
The second line in the preceding PHP code tells the computer that the $yourage
variable references the $myage variable, so whatever value the $myage variable
contains from now on will automatically get stored in the $yourage
variable.
After the third line, the $myage variable now contains the value of 109, so
the $yourage variable contains 109 too.