Variables

Variables hold the data that your program manipulates while it runs, such as information about a user that you've loaded from a database or entries that have been typed into an HTML form. In PHP, variables are denoted by $ followed by the variable's name. To assign a value to a variable, use an equals sign (=). This is known as the assignment operator.
$plates = 5;
$dinner = 'Beef Chow-Fun';
$cost_of_dinner = 8.95;
$cost_of_lunch = $cost_of_dinner;
Assignment works with here documents as well:
$page_header = <<

Dinner

HTML_HEADER;

$page_footer = <<

HTML_FOOTER;
Variable names must begin with letter or an underscore. The rest of the characters in the variable name may be letters, numbers, or an underscore. Table 2-2 lists some acceptable variable names.

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