Obviously, the first thing you need in a dynamically-driven site is a database connection. You could use PHP's mysql_* functions, but this ties you to a MySQL database. A much better idea is to abstract common functions. If the site moves to a new database, these can be rewritten without altering the rest of your code.

All of my sites start off with an include('database.php'); line. This file is a class that handles all of the basic SQL functions. I'll go over them first, and then describe some methods of using them effectively. These functions were originally written by a colleague of mine, which I then wrapped in a class for integration with my own systems.

db_connect()

function db_connect(){
	// connects to the db server and selects a database
	// provides $con as the database connection

	$host = "localhost";	// host ip or name
	$user = "username";	// username
	$pass = "password";	// password
	$db	= "database";	// database to select

	if( !$con = mysql_connect($host, $user, $pass) ){
		return 0;
	}

	if( !mysql_select_db($db, $con) ){
		return 0;
	}else{
		return $con;
	}
}

db_connect() is simple enough. It simply connects to a specific host with a user/pass combo, and selects a database to use. It returns $con as the identifier for the PHP connection - we'll use this later.

execute_sql($con,$sql)

function execute_sql( $con, $sql ){
	// $con is a valid DB resource.
	// $sql is the sql query to run.

	// Success will return a valid result set
	// Failure will return false

	if( !$res = mysql_query($sql, $con) ){
		return 0;
	}else{
		return $res;
	}
}

execute_sql() is another easy one. It simply runs a SQL query and returns a response if necessary. If you're just running a straightforward query (such as INSERT or UPDATE) you won't need the result. But if you're selecting records and need the recordset, you can assign the return to a variable.

num_results()

function num_results($res){
	// $res is a valid resultset

	// Returns the number of rows in $res
	// On error will return false
	return mysql_num_rows($res);
}

num_results() simply counts the results in a recordset returned from execute_sql().

get_result()

function get_result( $res, $row, $field ){
	// $res is a valid result set.
	// $row is an integer value of the row which 
	// contains the result to be fetched.
	// $field is the name of the field to be returned.
	
	return mysql_result( $res, $row, $field );

}

Finally, get_result() is used to grab the data in any specified field on any specified row.

These functions are wrapped in a class called db. At the end of the file, after the class, I declare the class like this:

$db = new db();
$con = $db->db_connect();

Now, I have $con as a connection identifer that I can access from any function throughout the site. On the next page I'll go through how I use the functions for accessing any database information.