Hour 8. Interacting with MySQL Using PHP

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Connecting to MySQL with PHP

To successfully use the PHP functions to talk to MySQL, you must have MySQL running at a location to which your

Web server can connect (not necessarily the same machine as your Web server). You also must have created a user

(with a password), and you must know the name of the database to which you want to connect. If you followed the

instructions in Hour 1, "Installing and Configuring MySQL," and Hour 3, "Installing and Configuring PHP," you

should already have taken care of this.



In all sample scripts in this hour, the sample database name is testDB, the sample user is joeuser, and the sample

password is somepass. Substitute your own information when you use these scripts.



You can find the section of the PHP Manual that covers all MySQL-related functions at

http://www.php.net/manual/en/ref.mysql.php. Use it!



Using mysql_connect()

The mysql_connect() function is the first function you must call when utilizing a PHP script to connect to

MySQL—without an open connection to MySQL, you won't get very far! The basic syntax for the connection is

mysql_connect("hostname", "username", "password");



Using actual sample values, the connection function looks like this:

mysql_connect("localhost", "joeuser", "somepass");



This function returns a connection index if the connection is successful or returns false if the connection fails. Listing

8.1 is a working example of a connection script. It assigns the value of the connection index to a variable called

$conn, then prints the value of $conn as proof of a connection.

Listing 8.1 A Simple Connection Script

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$conn = mysql_connect("localhost", "joeuser", "somepass");

echo "$conn";

?>



Save this script as mysqlconnect.php and place it in the document area of your Web server. Access the script with

your Web browser and you will see something like the following in your Web browser:

Resource id #1



Connecting to MySQL using the mysql_connect() function is pretty straightforward. The connection closes when the

script finishes its execution, but if you would like to explicitly close the connection, simply add the mysql_close()

function at the end of the script, as in Listing 8.2.



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Working with MySQL Data

Inserting, updating, deleting, and retrieving data all revolve around the use of the mysql_query() function to execute

the basic SQL queries. For INSERT, UPDATE, and DELETE, no additional scripting is required after the query has

been executed because you're not displaying any results (unless you want to). For SELECT, you have a few options

for displaying the data retrieved by your query. Let's start with the basics and insert some data, so you'll have

something to retrieve later on.



Inserting Data with PHP

The easiest method for inserting data is to simply hard-code the INSERT statement, as shown in Listing 8.6.

Listing 8.6 A Script to Insert a Record

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// open the connection

$conn = mysql_connect("localhost", "joeuser", "somepass");

// pick the database to use

mysql_select_db("testDB",$conn);

// create the SQL statement

$sql = "INSERT INTO testTable values ('', 'some value')";

// execute the SQL statement

$result = mysql_query($sql, $conn) or die(mysql_error());

// echo the result identifier

echo $result;

?>



You might wonder why you need to echo the result identifier if you're just inserting data. Well, you don't have to; it's

just there for kicks. You can clean this script up a bit by replacing the query execution line so that it simply executes

and prints a relevant statement if successful, as shown in Listing 8.7.

Listing 8.7 The Modified Insert Script

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// open the connection

$conn = mysql_connect("localhost", "joeuser", "somepass");

// pick the database to use

mysql_select_db("testDB",$conn);

// create the SQL statement

$sql = "INSERT INTO testTable values ('', 'some value')";

// execute the SQL statement

if (mysql_query($sql, $conn)) {

echo "record added!";

} else {

echo "something went wrong";

}

?>



Running this script will result in the addition of a row to the testTable table. To enter more records than just the one

shown in the script, you can either make a long list of hard-coded SQL statements and use mysql_query() multiple

times to execute these statements, or you can create a form-based interface to the record addition script.



To create the form for this script, you really only need one field because the id field can automatically increment. The

action of the form is the name of the record-addition script; let's call it insert.php. Your HTML form might look



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Summary

Using PHP and MySQL to create dynamic, database-driven Web sites is a breeze. Just remember that the PHP

functions are essentially a gateway to the database server; anything you'd enter using the MySQL command-line

interface, you can use with mysql_query().



To connect to MySQL with PHP, you need to know your MySQL username, password, and database name. Using

mysql_connect() and mysql_select_db(), you can connect to and select a database to use throughout the life of the

script.



Once connected, you can issue standard SQL commands with the mysql_query() function. If you have issued a

SELECT command, you can use mysql_numrows() to count the records returned in the resultset. If you want to

display the data found, you can use mysql_fetch_array() to get all the results during a loop and display them onscreen.

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Workshop

The workshop is designed to help you anticipate possible questions, review what you've learned, and begin to put

your knowledge into practice.



Quiz



1:

What is the primary function used to make the

connection between PHP and MySQL, and what

information is necessary?

A1:

The mysql_connect() function creates a connection to

MySQL and requires the hostname, username, and

password.

2:

Which PHP function retrieves a MySQL error

message?

A2:

The mysql_error() function returns a MySQL error

message.

3:

Which PHP function is used to count the number of

records in a resultset?

A3:

The mysql_numrows() function counts the number of

records in a resultset.



Activity

Create a PHP script that displays the contents of the grocery_inventory table that was used in the previous hour.

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Part III: Getting Involved with

the Code

Hour



9 Working with Forms

10 Working with Files

11 Working with Dates and Times

12 Creating a Simple Calendar

13 Working with Strings

14 Creating a Simple Discussion Forum

15 Restricting Access to Your Applications

16 Working with User Sessions

17 Logging and Monitoring Server Activity

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Hour 9. Working with Forms

Until now, the PHP examples in this book have been missing a crucial dimension. Sure, you know the basics, can set

variables and arrays, create and call functions, and connect to MySQL to do great things with a database. But that's

all meaningless if users can't reach into a language's environment to offer it information. In this hour, you look at

strategies for acquiring and working with user input. On the World Wide Web, HTML forms are the principal means

by which substantial amounts of information pass from the user to the server.



In this hour, you will learn

•

How to access information from form fields

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How to work with form elements that allow multiple selections

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How to create a single document that contains both an HTML form and the PHP code that handles its

submission

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How to save state with hidden fields

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How to redirect the user to a new page

•

How to build HTML forms and PHP code that send mail

•

How to build HTML forms that upload files and how to write the PHP code to handle them

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