1. PHP: Database connection
FdSc Module 109
Server side scripting and
Database design
2011

2. Connecting PHP to MySQL
MySQL connection is done with the function
mysql_connect
Selecting a database is done with the function
mysql_select_db

3. mysql_connect This needs three parameters: The host name The user name
The password
Use the following variables and set their values appropriately:
$hostname = “localhost";
$username = “MISNumber";
$password = "YOUR_PASSWORD";

4. PHP variables All PHP variables must Start with $
Contain alphanumeric characters or the underscore
Must begin with a letter or an underscore
$username = “MISNumber" both declares and assigns the value to the variable
PHP is loosely typed: variables do not need separate declaration

5. mysql_connect Mysql_connect is a function
It takes three parameters and returns a value
Either a valid SQL link identifier which PHP sees as TRUE
Or FALSE if the connection failed
$dbConnected = mysql_connect($hostname, $username, $password);
The returned value will be assigned to the variable $dbConnected
If successful we will use it later
If it fails we will trap the error

6. mysql_select_db This needs two parameters: The database name
The valid SQL link identifier returned from mysql_connect
Use the following variable and set its value appropriately:
$databaseName = “MISNumber_library";
$dbSelected = mysql_select_db ($databaseName,$dbConnected);
$dbSelected will be TRUE if the database has been selected

7. connection.php <?php
//error_reporting(0); // Suppresses MySQL error messsages. Can also in front of each command.
$hostname = “localhost";
$username = “MISNumber";
//$password = "YourPassword";
//$databaseName = “MISNumber_library";
$dbConnected = mysql_connect($hostname, $username, $password);
$dbSelected = mysql_select_db ($databaseName,$dbConnected);
if ($dbConnected) {
echo "MySQL connected OK<br /><br />"; //HTML syntax can be included in the echo string
if ($dbSelected) {
echo "DB Connected OK<br /><br />";
} else {
echo "DB Connected FAILED<br /><br />"; }
echo "MySQL connection FAILED<br /><br />";
?>

8. File headers
It is important to document what each php script does in a file header
We can use a comment block to do this
We start a comment block with
/* and end it with */
This allows multi line comments
Single line comments just start with //

9. File header example
/* File: connection.php By: Bob Date: This script connects to a database */