This will display categories in Wordpress, note that for SEO an <H1> tag would be better for the categories text.

<h2>Categories</h2>
<ul>
<?php wp_list_cats('sort_column=name'); ?>
</ul>

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:
1.The inability to index the data. This makes it necessary to potentially read ALL the data sequentially. This is a major problem if there are a lot of records in the flat file because the time required to read the flat file is proportionate to the number of records in the flat file.
2.The inability to efficiently control access by users to the data
3.The inefficient storage of the data. In most cases, the data would not be encrypted or compressed as this would exacerbate the problem no. 1 above

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:
1.Connect to a MySQL database
2.Execute standard SQL statements against the MySQL database

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!

Developing a Login System with PHP and MySQL

Most interactive websites nowadays would require a user to log in into the website’s system in order to provide a customized experience for the user. Once the user has logged in, the website will be able to provide a presentation that is tailored to the user’s preferences.

A basic login system typically contains 3 components:
1. The component that allows a user to register his preferred login id and password
2. The component that allows the system to verify and authenticate the user when he subsequently logs in
3. The component that sends the user’s password to his registered email address if the user forgets his password

Such a system can be easily created using PHP and MySQL.

================================================================

Component 1 – Registration

Component 1 is typically implemented using a simple HTML form that contains 3 fields and 2 buttons:
1. A preferred login id field
2. A preferred password field
3. A valid email address field
4. A Submit button
5. A Reset button

Assume that such a form is coded into a file named register.html. The following HTML code excerpt is a typical example. When the user has filled in all the fields, the register.php page is called when the user clicks on the Submit button.

[form name="register" method="post" action="register.php"]
[input name="login id" type="text" value="loginid" size="20"/][br]
[input name="password" type="text" value="password" size="20"/][br]
[input name="email" type="text" value="email" size="50"/][br]
[input type="submit" name="submit" value="submit"/]
[input type="reset" name="reset" value="reset"/]
[/form]

The following code excerpt can be used as part of register.php to process the registration. It connects to the MySQL database and inserts a line of data into the table used to store the registration information.

@mysql_connect(”localhost”, “mysql_login”, “mysql_pwd”) or die(”Cannot connect to DB!”);
@mysql_select_db(”tbl_login”) or die(”Cannot select DB!”);
$sql=”INSERT INTO login_tbl (loginid, password and email) VALUES (”.$loginid.”,”.$password.”,”.$email.”)”;
$r = mysql_query($sql);
if(!$r) {
$err=mysql_error();
print $err;
exit();
}

The code excerpt assumes that the MySQL table that is used to store the registration data is named tbl_login and contains 3 fields – the loginid, password and email fields. The values of the $loginid, $password and $email variables are passed in from the form in register.html using the post method.

================================================================

Component 2 – Verification and Authentication

A registered user will want to log into the system to access the functionality provided by the website. The user will have to provide his login id and password for the system to verify and authenticate.

This is typically done through a simple HTML form. This HTML form typically contains 2 fields and 2 buttons:
1. A login id field
2. A password field
3. A Submit button
4. A Reset button

Assume that such a form is coded into a file named authenticate.html. The following HTML code excerpt is a typical example. When the user has filled in all the fields, the authenticate.php page is called when the user clicks on the Submit button.

[form name="authenticate" method="post" action="authenticate.php"]
[input name="login id" type="text" value="loginid" size="20"/][br]
[input name="password" type="text" value="password" size="20"/][br]
[input type="submit" name="submit" value="submit"/]
[input type="reset" name="reset" value="reset"/]
[/form]

The following code excerpt can be used as part of authenticate.php to process the login request. It connects to the MySQL database and queries the table used to store the registration information.

@mysql_connect(”localhost”, “mysql_login”, “mysql_pwd”) or die(”Cannot connect to DB!”);
@mysql_select_db(”tbl_login”) or die(”Cannot select DB!”);
$sql=”SELECT loginid FROM login_tbl WHERE loginid=’”.$loginid.”’ and password=’”.$password.”’”;
$r = mysql_query($sql);
if(!$r) {
$err=mysql_error();
print $err;
exit();
}
if(mysql_affected_rows()==0){
print “no such login in the system. please try again.”;
exit();
}
else{
print “successfully logged into system.”;
//proceed to perform website’s functionality – e.g. present information to the user
}

As in component 1, the code excerpt assumes that the MySQL table that is used to store the registration data is named tbl_login and contains 3 fields – the loginid, password and email fields. The values of the $loginid and $password variables are passed in from the form in authenticate.html using the post method.

================================================================

Component 3 – Forgot Password

A registered user may forget his password to log into the website’s system. In this case, the user will need to supply his loginid for the system to retrieve his password and send the password to the user’s registered email address.

This is typically done through a simple HTML form. This HTML form typically contains 1 field and 2 buttons:
1. A login id field
2. A Submit button
3. A Reset button

Assume that such a form is coded into a file named forgot.html. The following HTML code excerpt is a typical example. When the user has filled in all the fields, the forgot.php page is called when the user clicks on the Submit button.

[form name="forgot" method="post" action="forgot.php"]
[input name="login id" type="text" value="loginid" size="20"/][br]
[input type="submit" name="submit" value="submit"/]
[input type="reset" name="reset" value="reset"/]
[/form]

The following code excerpt can be used as part of forgot.php to process the login request. It connects to the MySQL database and queries the table used to store the registration information.

@mysql_connect(”localhost”, “mysql_login”, “mysql_pwd”) or die(”Cannot connect to DB!”);
@mysql_select_db(”tbl_login”) or die(”Cannot select DB!”);
$sql=”SELECT password, email FROM login_tbl WHERE loginid=’”.$loginid.”’”;
$r = mysql_query($sql);
if(!$r) {
$err=mysql_error();
print $err;
exit();
}
if(mysql_affected_rows()==0){
print “no such login in the system. please try again.”;
exit();
}
else {
$row=mysql_fetch_array($r);
$password=$row["password"];
$email=$row["email"];

$subject=”your password”;
$header=”from:you@yourdomain.com”;
$content=”your password is “.$password;
mail($email, $subject, $row, $header);

print “An email containing the password has been sent to you”;
}

As in component 1, the code excerpt assumes that the MySQL table that is used to store the registration data is named tbl_login and contains 3 fields – the loginid, password and email fields. The value of the $loginid variable is passed from the form in forgot.html using the post method.

================================================================

Conclusion

The above example is to illustrate how a very basic login system can be implemented. The example can be enhanced to include password encryption and additional functionality – e.g. to allow users to edit their login information.

About the Author

Used with the author’s permission.
This article is written by daBoss. daBoss is the Webmaster of Designer Banners (http://www.designerbanners.com). daBoss can be contacted at sales (at) designerbanners (dot) com.

First off, if you read last week’s article by me (the one about site personalization in PHP), I have one addition to make to make your life a little easier. If you didn’t read last week’s article, read it. It’ll help you. You can find it here: http://jumpx.com utorials/1

Now, remember how we personalized a page for your visitor? This works fine, but what do we do if they didn’t use that special link, and just went to the page?

What I’m saying is, if you special personalized page was at http://www.your.host/sales.php/f=Oscar/l=Grouch but your visitor only went to http://www.your.host/sales.php. Instead of the name there would just be a blank spot! Last week I forgot to cover this.

All we have to do to fix it is to tell PHP that if they didn’t leave a name, to substitute one in for them. So let’s say that if they left their first name blank to make their first name “Friend”. This way instead of saying “Dear Oscar:” it would say “Dear Friend:”.

Put the following line of code JUST ABOVE THE LINE that says something similar to: echo “$f $l” :

if ($f == “”) { $f = “Friend”; }

That way, you can use your special personalized page as a normal page and no one will be the wiser.

Password protection is something you need every once in a while. Whether it’s a secret site you’re running or just the control panel of your favorite script.

Sometimes you don’t need a fancy solution like .htaccess if you’re only worrying about a single user (you). But JavaScript passwords can be worked around, and HTML-based passwords based on cookies, written in PHP are complicated and take time to write. Htaccess is nice but it’s a pain if you just want to use it for one person.

Here is a simple way to use HTTP authentication (the same you see used by htaccess) with just a few lines of code. Below are the sample contents of a file you can use.

$myusername = “myusername”;
$mypassword = “mypassword”;
$areaname = “My Protected Area”;

if ($PHP_AUTH_USER == “” || $PHP_AUTH_PW == “” || $PHP_AUTH_USER != $myusername || $PHP_AUTH_PW != $mypassword) {
header(”HTTP/1.0 401 Unauthorized”);
header(”WWW-Authenticate: Basic realm=”$areaname”");
echo ”

Authorization Required.

“;
die();
}

?>

my main text.

Last week we learned that PHP code can be integrated into your HTML. All you have to do is make sure the file ends in .php (for example, “firehydrant.php”) and it will work. Everything that comes in between this:

/* And this: */

?>

Is treated as PHP code. Everything outside of those tags is treated as plain HTML.

When copying this code over be SURE to include that last line where it says “my main text.” Note that “my main text” is located outside of the PHP code brackets. This means that where you see “my main text” can be your normal HTML file!

Take all of this code and Upload the script onto your web server and run it in the browser. You should be greeted by a password popup box similar to those you see with htaccess. Enter “myusername” as the username and “mypassword” as the password. You should be given a page that says “my main text” and nothing else.

Close your browser window (this is very important) and going back to that page. Try entering the wrong info. The box will come up again. You have three tries and then are given that dreadful “Authorization Required” message.

If you want to take the next step, go back to your code and change “myusername” and “mypassword” to a username and password of your choice. Upload it back to your web server and try again. Now go to that page again and you’ll see that you can only be let in using the username and password you chose for yourself.

Now change the part that says “My Protected Area” to something else, say “John Calder’s Bar and Grill.” Upload and try it. You’ll see when that password box comes up under “Realm” it’ll say “John Calder’s Bar and Grill.” You can change this to whatever you like.

But what if you want to password protect just a handful of files? Do you have to copy and paste this code onto PHP script after PHP script?

Hell no!

Take the code you just modified and take the last line out of it. You know, the one that said “my main text.” All you should have in there now is everything in between the PHP brackets ().

Save this file as “auth.php”. You can rename this later, on your own time.

Make a new file called “test.php” or just rename one of your normal HTML to this name. It doesn’t matter. At the very top of test.php (the VERY top, meaning the first line) copy and paste this line of code:

Upload auth.php and test.php to your web server and run test.php. Make sure both files are placed in the same folder. Now, try to go to test.php in your web browser. You’ll see that you can’t get to test.php without the right username and password. You can do this to any file with a “.php” extension just by adding that one line of code.

The catch to it is that this line of code has to be at the very top of the file. On the very first line. The reason for this is that when the script asks for a person’s username and password, these are sent using HTTP headers and *must* come before anything else.

Of course, this doesn’t take care of your secret sites or private members’ areas, where you have to deal with several logins, but that’s what htaccess is for.

While we’re on the subject of includes, one last thing before we finish up.

Includes are basically a way of absorbing other files into your script. As you saw when we included auth.php, the script read everything that was in auth.php and used it as if the contents of that file were actually there. This works with not only PHP scripts but also with other files as well.

Make a new file called “header.html”. Put anything you want in it, but I just put “This is my header
” when I did it.

Make a second file called “footer.html”. Again, go again and put anything you want in it, but I just put “This is my footer
” in.

Make a third file called “main.php.” Copy the following into it.

This is my main page

Upload all three into the same folder and run main.php. You should see the following:

This is my header
This is my main page
This is my footer

This is just a basic example of how includes can be used. But if you have a web site with several pages and the same layout… wouldn’t it be easier just to put everything above your main text in header.html and everything below that main text in footer.html? That way if you change your design you only have to edit 2 files instead of 100 or 200?

You’d think.

About the Author

Article by Robert Plank

Free PHP articles and advice.
http://www.jumpx.com/newsletter

Introduction
Cookies have long been used in PHP scripts, and are a very useful function. But what exactly are cookies? Maybe you have used then, but you still don’t know exactly what they are. Or you are completely new to cookies? It doesn’t matter, because in this tutorial I will show you exactly what cookies are, and what they are used for.

Cookies in a nutshell
Cookies are small pieces of information that is stored on the computer of your visitors. Each browser handles it differently, but most simply store the information in a small text file. Internet Explorer has a special folder, which can be found in your C:Windows or C:WindowsSystem32 folder. You can delete all your cookies, by going to the Options and ‘Clearing Cookies’ or deleting them by hand. I don’t recommend this though.

Almost every website uses cookies. If you go to Amazon.com, you will get several cookies. The same goes for CNN.com. Even Google uses cookies! They are extremely useful for (temporarily) storing information. For example, if you have a login system for your visitors, you could save their userid and password (very heavily encrypted!) so they are automatically logged in the next time they visit your website.

Or you could remember their last visit, and highlight everything that is new. And that’s just the beginning.

Using Cookies
Using cookies in PHP is extremely easy. In fact, there is nothing to it, because of PHP’s inbuilt setcookie() function. Have a look at the documentation, and then try the following example:

<?php

// Set a cookie
// Cookie name: name
// Cookie value: Dennis Pallett
// Cookie expire: in 24 hours

setcookie (’name’, ‘Dennis Pallett’, time() + (60*60*24));
?>

If you run the code above, then a cookie will be set. That’s all. The cookie name and value are pretty obvious. The cookie expire is when the cookie expires, or goes away. Simply use the time() function and add the number of seconds you want to have the cookie available to it. In the example I added 60*60*24=86400 seconds, or 24 hours.

If you have looked at the documentation, you probably noticed there are additional arguments. As the documentation says, the path is to limit a cookie to a specific path on your web server. This is often used when you run multiple instances of the same script in separate directories. You can safely omit this argument when it doesn’t matter if the cookie is available site-wide.

There is also the domain argument. This can be used to limit the cookie to a specific sub-domain, e.g. test.example.com. You can also safely ignore this argument, or set it to .example.com (note the beginning period, this is essential!).

Finally, there is also the secure argument. This argument is only used for cookies that are sent over a secure HTTPS connection (SSL). Just ignore this argument, unless you’re working with a secure connection.

One thing that should be mentioned is that cookies must be set, before you display any HTML/text. It’s probably best if you turn on output buffering by putting ob_start() at the top of your page.

Now that you have set a cookie, you probably want to retrieve the value as well. After all, that is the whole point of using cookies. Thankfully, as PHP is ever so easy, you can retrieve the same way as you retrieve a GET value. See the following example to retrieve the value of the previous example:

<?php
echo ‘Your name is ‘ . $_COOKIE['name'];
?>

This should print “Your name is Dennis Pallett”. There’s nothing more to it. It’s just that easy!

Finally, one thing you probably want to do as well is remove cookies. This is as easy as setting them. Simply change the value of the cookie to FALSE, and change the expire date to -3000 seconds. See the following example:

<?php
setcookie (’name’, FALSE, time()-1000);
?>

Checking if cookies are enabled
Before you start using cookies, you must make sure your visitor has cookies enabled. This can be done with a simply PHP checking script. Unfortunately, the PHP page needs to reload to check for cookies. But this can be done very transparently, and your visitor should hardly notice anything.

The following example will first set a test cookie, then reload the page, and finally check whether cookies are enabled.

<?php
error_reporting (E_ALL ^ E_WARNING ^ E_NOTICE);

// Check if cookie has been set or not
if ($_GET['set'] != ‘yes’) {
// Set cookie
setcookie (’test’, ‘test’, time() + 60);

// Reload page
header (”Location: checkcookies.php?set=yes”);
} else {
// Check if cookie exists
if (!empty($_COOKIE['test'])) {
echo “Cookies are enabled on your browser”;
} else {
echo “Cookies are <b>NOT</b> enabled on your browser”;
}
}
?>

Run the code above, and see what the output is. Check if cookies are enabled in your browser. If they’re not enabled, then you can enable them by going to your browser’s options. Unfortunately, this is different from each browser, so I can’t give you exact instructions. But Google can.

Storing Arrays
One feature of cookies that is often missed in articles is the ability to story arrays. Cookies can be used to store multi-dimensional arrays, which can be extremely useful to store data.

Consider the following code;

<?php
setcookie (”name[first]“, “Dennis”, time() + (60*60*24));
setcookie (”name[last]“, “Pallett”, time() + (60*60*24));
?>

You can then display these two cookies using the following code:

<?php
echo “First Name: ” . $_COOKIE['name']['first'];
echo “<br />Last Name: ” . $_COOKIE['name']['last'];
?>

The cookie ‘name’ is an array, and has multiple values. You can even go deeper and have multi-dimensional arrays, e.g. $_COOKIE['name']['test']['something']['value']. You could store whole arrays of data in cookies. But beware that you don’t store too much data, there are certain size limits to cookies.

In Conclusion…
Cookies are really versatile, and can be used for a lot of different purposes. Many websites use cookies, and cookies can really make your website more personalized. Using cookies in PHP isn’t hard at all, and you should be able to use them without any difficulty.

Before actively using cookies in your website, you must check whether the visitor has enabled them in their browser. If they don’t have cookies enabled, you must either redirect to a non-cookies version of your website, or you can make sure your website also works without cookies.

You can download a sample script at http://www.phpit.net/demo/php%20and%20cookies/logger.zip, where cookies are used in a (somewhat) practical way. In this example, there is a logging module, called log.php and a display module, called history.php. Basically, you include the log.php in other PHP pages, and then you can view history.php to lookup all the pages you have viewed and how often. The example uses arrays, and stores them in cookies.

The examples in this article can be downloaded at http://www.phpit.net/demo/php%20and%20cookies/examples.zip.

If you have a really unique practical way of using cookies, please let me know at dennis [AT] nocertainty [DOT] com. I’d really like to hear about interesting ways of using cookies.

About the Author

Dennis Pallett is a young tech writer, with much experience in ASP, PHP and other web technologies. He enjoys writing, and has written several articles and tutorials. To find more of his work, look at his websites at http://www.phpit.net, http://www.aspit.net and http://www.ezfaqs.com