PHP/MySQL Cheat Sheet
There is a lot to learn about the interaction between PHP and MySQL.
But the basic tools can be covered relatively quickly. This handout is
designed to be a quick-reference guide for the most important features of
PHP and MySQL.
Identifying PHP code
PHP code intermixed with HTML is delimited by the tags <?php ... ?>. PHP
statements end with a semi-colon.
Variables
Variables are simply names used in PHP to store values. They are indicated by a string
preceded by a dollar sign. For instance, the following statement assigns the value
“CSC111” to the variable $course_number:
$course_number = “CSC111”;
Variables in PHP do not have to be declared before they can be used.
Output
Information is written to the browser window in PHP using the echo or print
command. The two commands are interchangeable. HTML tags mixed in with the
output to be printed are interpreted appropriately. The period character (“.”) is used to
concatenate parts of output strings together. For example:
echo “The sum of ” . $num1 . “ and ” . $num2 . “ is ” . $sum . “.”;
As long as you use double-quotes, you can simplify statements like this by including the
variables within the quotes. Then the values of the variable will replace the variables
themselves. For instance, the statement:
echo “The sum of $num1 and $num2 is $sum”;
will print
The sum of 3 and 5 is 8
assuming $num1=3, $num2=5 and $sum=8.
Getting Information from HTML Forms
Extracting information from HTML forms is very easy in PHP. If a PHP page is given as
the action to be carried out when a form is submitted, that page can access the fields of
the form from a special global array simply by using the field names of the form as
indices. For instance, if your form has fields called FirstName and LastName, the
PHP page that processes the form can access them using $_POST["FirstName"] and
$_POST["LastName"], which will contain whatever the user entered into the
corresponding fields in the form. (NOTE: This assumes that the POST method was used
in the form. Use $_GET if the GET method was used instead. See below for more.)
Getting Information from the URL
Using the GET method rather than the POST method with your form will cause all of the
form values to be appended to the end of the URL of the PHP page as a querystring when
the form is submitted. For instance:
http://cs.furman.edu/csc111.php?fName=Joe&lName=Cool
PHP handles querystrings just as it handles form input sent by the POST method – it
simply places the values in a different global array. So, given the URL above, the page
