Most interactive websites nowadays require data to be presented dynamically and interactively based on input from the user. For example, a customer may need to log into a retail website to check his purchasing history. In this instance, the website would have stored two types of data in order for the customer to perform the check ? the customer's personal login details; and the customer's purchased items. This data can be stored in two types of storage ? flat files or databases.
Flat files are only feasible in very low to low volume websites as flat files have 3 inherent weaknesses:
The alternative which is, in my opinion, the only feasible method, is to store the data in a database. One of the most prevalent databases in use is MySQL. Data that is stored in a database can easily be indexed, managed and stored efficiently. Besides that, most databases also provide a suite of accompanying utilities that allow the database administrator to maintain the database ? for example, backup and restore, etc.
Websites scripted using PHP are very well suited for the MySQL database as PHP has a custom and integrated MySQL module that communicates very efficiently with MySQL. PHP can also communicate with MySQL through the standard ODBC as MySQL is ODBC-compliant, However, this will not be as efficient as using the custom MySQL module for PHP.
The rest of this article is a tutorial on how to use PHP to:
Starting a Session with MySQL
Before the PHP script can communicate with the database to query, insert or update the database, the PHP script will first need to connect to the MySQL server and specify which database in the MySQL server to operate on.
The mysql_connect() and mysql_select_db() functions are provided for this purpose. In order to connect to the MySQL server, the server name/address; a username; and a valid password is required. Once a connection is successful, the database needs to be specified.
The following 2 code excerpts illustrate how to perform the server connection and database selection:
@mysql_connect("[servername]", "[username]", "[password]") or die("Cannot connect to DB!");
@mysql_select_db("[databasename]") or die("Cannot select DB!");
The @ operator is used to suppress any error messages that mysql_connect() and mysql_select_db() functions may produce if an error occurred. The die() function is used to end the script execution and display a custom error message.
Executing SQL Statements against a MySQL database
Once the connection and database selection is successfully performed, the PHP script can now proceed to operate on the database using standard SQL statements. The mysql_query() function is used for executing standard SQL statements against the database. In the following example, the PHP script queries a table called tbl_login in the previously selected database to determine if a username/password pair provided by the user is valid.
Assumption:
The tbl_login table has 3 columns named login, password, last_logged_in. The last_logged_in column stores the time that the user last logged into the system.
// The $username and $passwd variable should rightly be set by the login form
// through the POST method. For the purpose of this example, we're manually coding it.
$username = "john";
$passwd = "mypassword";
// We generate a SELECT SQL statement for execution.
$sql="SELECT * FROM tbl_login WHERE login = '".$username."' AND password = '".$passwd."'";
// Execute the SQL statement against the currently selected database.
// The results will be stored in the $r variable.
$r = mysql_query($sql);
// After the mysql_query() command executes, the $r variable is examined to
// determine of the mysql_query() was successfully executed.
if(!$r) {
$err=mysql_error();
print $err;
exit();
}
// If everything went well, check if the query returned a result ? i.e. if the username/password
// pair was found in the database. The mysql_affected_rows() function is used for this purpose.
// mysql_affected_rows() will return the number of rows in the database table that was affected
// by the last query
if(mysql_affected_rows()==0){
print "Username/password pair is invalid. Please try again.";
}
else {
// If successful, read out the last logged in time into a $last variable for display to the user
$row=mysql_fetch_array($r);
$last=$row["last_logged_in"];
print "Login successful. You last logged in at ".$last.".";
}
The above example demonstrated how a SELECT SQL statement is executed against the selected database. The same method is used to execute other SQL statements (e.g. UPDATE, INSERT, DELETE, etc.) against the database using the mysql_query() and mysql_affected_rows() functions.
About The Author
This PHP scripting article is written by John L. John L is the Webmaster of The Ultimate BMW Blog! (http://www.bimmercenter.com).
The Ultimate BMW Blog!
custom home cleaning Winnetka ..The internet has taken over our lives with a vengeance,... Read More
The Disability Discrimination Act says that websites must be made... Read More
Mini Websites are the most powerful and cost effective solution... Read More
cPanel is a control panel for your website and allows... Read More
Your web site will be your window to the world.... Read More
Building a new website can be a lengthy task. From... Read More
So you have a good idea for a business and... Read More
People often come to me in a state of crisis... Read More
There are many different traffic analysis tools, ranging from simple... Read More
Here's something you may never have thought of before:If I... Read More
When I set up my website I felt paypal was... Read More
Starting a business online is no longer as difficult as... Read More
There are millions and millions of websites on the Internet.... Read More
Just starting out, you can start with a simple informational... Read More
"How do I improve web site sales figures?" The CEO... Read More
"Build it and they will come."--Filed of Dreams (1989) If... Read More
How can we add Word Rich Content to our Websites... Read More
Many millions of dollars are being wasted on promoting and... Read More
Let's begin by setting some limits. If you're like me,... Read More
After years of working with entrepreneurs who developed their first... Read More
Part of the success of most home-based businesses is their... Read More
Globalize Your WebsiteThe Internet has unlocked a wide array of... Read More
Even with the steady growth of the World Wide Web,... Read More
Fantastico is a 3rd-party cPanel add-on and can be purchased... Read More
You want to give your site's visitors a way to... Read More
professional home cleaners Glenview ..Just starting out, you can start with a simple informational... Read More
Keywords in Search Engine Optimizing and Search Engine Marketing are... Read More
80% of your Web site is Maintenance!Once your Web site... Read More
I am just a learner who likes to delve in... Read More
SiteSpinnerSiteSpinner is a user-friendly web site development tool that includes... Read More
It may come as some surprise to a traditionally off-line... Read More
Building a new website can be a lengthy task. From... Read More
Like wine cars get more attractive to collectors as years... Read More
Launching a new small business website is often a long... Read More
What is SQL? SQL stands for Structured Query Language and... Read More
Alternate medicine finds its own place in the hearts and... Read More
What happened on your website yesterday? What about last week... Read More
Like most average persons, I wanted some extra money to... Read More
If you've been developing websites on Mars for the past... Read More
I had a client say something to me the other... Read More
You hear a great deal about the Internet these days... Read More
Is your website Really useful?I had a 'rep' in yesterday... Read More
People often come to me in a state of crisis... Read More
Although CSS layouts have been around for years, they haven't... Read More
There are many different traffic analysis tools, ranging from simple... Read More
The first thing my business consultant (read brother-in-law) asked me,... Read More
There are hundreds of millions of Web surfers today. Each... Read More
If you are like me you have wanted to build... Read More
So you've decided to start an online work at home... Read More
Every business needs to know how it is doing. That's... Read More
Web Development |