Page 72 - Beginning PHP 5.3

Part II: Learning the Language
As you might imagine, this code outputs the number 4 when it ’ s run. This is all well and good; however,
if you wanted to print the value of, say, 5 + 6 instead, you ’ d have to write another PHP script, as follows:
echo 5 + 6;

This is where variables come into play. By using variables instead of numbers in your script, you make
the script much more useful and flexible:

echo $x + $y;

You now have a general - purpose script. You can set the variables $x and $y to any two values you want,
either at some other place in your code, or as a result of input from the user. Then, when you run the
preceding line of code, the script outputs the sum of those two values. Re - run the script with different
values for $x and $y , and you get a different result.

Naming Variables

A variable consists of two parts: the variable ’ s name and the variable ’ s value. Because you ’ ll be using
variables in your code frequently, it ’ s best to give your variables names you can understand and
remember. Like other programming languages, PHP has certain rules you must follow when naming
your variables:

❑ Variable names begin with a dollar sign ( $ )
❑ The first character after the dollar sign must be a letter or an underscore
❑ The remaining characters in the name may be letters, numbers, or underscores without a
fixed limit

Variable names are case - sensitive ( $Variable and $variable are two distinct variables), so it ’ s worth
sticking to one variable naming method — for example, always using lowercase — to avoid mistakes.
It ’ s also worth pointing out that variable names longer than 30 characters are somewhat impractical.

Here are some examples of PHP variable names:
$my_first_variable
$anotherVariable
$x

$_123
Creating Variables

Creating a variable in PHP is known as declaring it. Declaring a variable is as simple as using its name in
your script:

$my_first_variable;
When PHP first sees a variable ’ s name in a script, it automatically creates the variable at that point.

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