237 Using a Generic Database Interface: PEAR DB is a standard for connections to databases. It has the most limited functionality of any of the function sets, for fairly obvious reasons. If you have to be compatible with every- thing, you can’t exploit the special features of anything. In addition to the libraries that come with PHP, database abstraction classes such as Metabase or PEAR::DB are available that allow you to use the same function names for each different type of database. Using a Generic Database Interface: PEAR DB We will look at a brief example using the PEAR DB abstraction layer.This is one of the core components of PEAR, and probably the most widely used of all the PEAR com- ponents. If you have PEAR installed, then you should already have DB. If not, please refer to the “PEAR Installation” section in Appendix A. For comparative purposes, let’s look at how we would have written our search results script differently using DB. Listing 10.5 results_generic.php—Retrieves Search Results from our MySQL Database and Formats Them for Display <html> <head> <title>Book-O-Rama Search Results</title> </head> <body> <h1>Book-O-Rama Search Results</h1> <?php // create short variable names $searchtype=$HTTP_POST_VARS['searchtype']; $searchterm=$HTTP_POST_VARS['searchterm']; $searchterm= trim($searchterm); if (!$searchtype || !$searchterm) { echo 'You have not entered search details. Please go back and try again.'; exit; } $searchtype = addslashes($searchtype); $searchterm = addslashes($searchterm); // set up for using PEAR DB require('DB.php'); $user = 'bookorama'; $pass = 'bookorama123'; $host = 'localhost'; 13 525x ch10 1/24/03 3:37 PM Page 237 238 Chapter 10 Accessing Your MySQL Database from the Web with PHP $db_name = 'books'; // set up universal connection string or DSN $dsn = "mysql://$user:$pass@$host/$db_name"; // connect to database $db = DB::connect($dsn, true); // check if connection worked if (DB::isError($db)) { echo $db->getMessage(); exit; } // perform query $query = "select * from books where ".$searchtype." like '%".$searchterm."%'"; $result = $db->query($query); // check that result was ok if (DB::isError($result)) { echo $db->getMessage(); exit; } // get number of returned rows $num_results = $result->numRows(); // display each returned row for ($i=0; $i <$num_results; $i++) { $row = $result->fetchRow(DB_FETCHMODE_ASSOC); echo '<p><strong>'.($i+1).'. Title: '; echo htmlspecialchars(stripslashes($row['title'])); echo '</strong><br />Author: '; echo stripslashes($row['author']); echo '<br />ISBN: '; echo stripslashes($row['isbn']); echo '<br />Price: '; echo stripslashes($row['price']); echo '</p>'; } // disconnect from database $db->disconnect(); Listing 10.5 Continued 13 525x ch10 1/24/03 3:37 PM Page 238 239 Using a Generic Database Interface: PEAR DB ?> </body> </html> Let’s examine what we are doing differently in this script. To connect to the database we use the line $db = DB::connect($dsn, true); This function accepts a universal connection string that contains all the parameters nec- essary to connect to the database.You can see this if you look at the format of the con- nection string: $dsn = "mysql://$user:$pass@$host/$db_name"; The second parameter to connect() determines whether the connection will be persist- ent or not. A value of true will make it persistent. After this, we check to see if connection was unsuccessful using the isError() method and, if so, print the error message and exit: if (DB::isError($db)) { echo $db->getMessage(); exit; } Assuming everything has gone well, we then set up a query and execute it as follows: $result = $db->query($query); We can check the number of rows returned: $num_results = $result->numRows(); We retrieve each row as follows: $row = $result->fetchRow(DB_FETCHMODE_ASSOC); The generic method fetchRow() can fetch a row in many different formats —the parameter DB_FETCHMODE_ASSOC tells it that we would like the row returned as an asso- ciative array. After outputting the returned rows, we finish by closing the database connection: $db->disconnect(); As you can see, this generic example is very similar to our first script. The advantages of using DB are that we only need to remember one set of database functions and that the code will require minimal changes if we decide to change our database software. Listing 10.5 Continued 13 525x ch10 1/24/03 3:37 PM Page 239 240 Chapter 10 Accessing Your MySQL Database from the Web with PHP Since this is a MySQL book we will use the MySQL native libraries for a little extra speed and flexibility.You might wish to use the DB package in your projects, however, as there are times when the use of an abstraction layer can be extremely helpful. Further Reading For more information on connecting MySQL and PHP together, you can read the appropriate sections of the PHP and MySQL manuals. For more information on ODBC, visit http://www.webopedia.com/TERM/O/ODBC.html Metabase is available from http://phpclasses.upperdesign.com/browse.html/package/20 Next In the next chapter, we will go into more detail about MySQL administration and dis- cuss how you can optimize your databases. 13 525x ch10 1/24/03 3:37 PM Page 240 11 Advanced MySQL IN THIS CHAPTER ,WE’LL COVER SOME more advanced MySQL topics including advanced privileges, security, and optimization. The topics we’ll cover are n Understanding the privilege system in detail n Making your MySQL database secure n Getting more information about databases n Speeding things up with indexes n Optimization tips n Different table types n Backup and recovery Understanding the Privilege System in Detail Previously (in Chapter 8,“Creating Your Web Database”) we looked at setting up users and granting them privileges.We did this with the GRANT command. If you’re going to administer a MySQL database, it can be useful to understand exactly what GRANT does and how it works. When you issue a GRANT statement, it affects tables in the special database called mysql.Privilege information is stored in five tables in this database. Given this, when granting privileges on databases, you should be cautious about granting access to the mysql database. One side note is that the GRANT command is only available from MySQL version 3.22.11 onward. We can look at what’s in the mysql database by logging in as an administrator and typing use mysql; 14 525x ch11 1/24/03 3:37 PM Page 241 . information on connecting MySQL and PHP together, you can read the appropriate sections of the PHP and MySQL manuals. For more information on ODBC, visit http://www.webopedia.com/TERM/O/ODBC.html Metabase. 239 240 Chapter 10 Accessing Your MySQL Database from the Web with PHP Since this is a MySQL book we will use the MySQL native libraries for a little extra speed and flexibility.You might wish to use the DB. DB. Listing 10.5 results_generic .php Retrieves Search Results from our MySQL Database and Formats Them for Display <html> <head> <title>Book-O-Rama Search Results</title> </head> <body> <h1>Book-O-Rama