Home > Articles > Programming > PHP

This chapter is from the book

This chapter is from the book

Using Pear::DB

Although PHP's DBX functions are useful on simple sites, there is a more feature-rich solution available for sites that require greater complexity in their database use. This solution is PEAR::DB.

PEAR—PHP Extension and Application Repository

PEAR is a "framework and distribution system for reusable PHP components."1 PEAR provides "modules" along the lines of the PERL CPAN module set. Think of the modules as libraries of prebuilt components that you can use to make your PHP coding easier. PEAR is currently in beta and is under heavy development, but it already contains many useful modules that you can use in your own projects. PEAR provides open-source modules, distribution and maintenance for those modules, and a coding standard for said modules.

PEAR is distributed with PHP. If you've installed PHP recently, you may have noticed the "pear" directory and the many files that it contains. Since PEAR is still in beta, it hasn't been widely advertised, but it has begun to get a lot of attention from PHP developers, especially those who have been using third-party libraries, such as PHPLIB and ADOdb. Although there are good third-party libraries available, there is not yet a standard as far as coding guidelines, distribution, and maintenance. PEAR looks to be the solution to this problem.

One of the modules that is starting to gain a lot of popularity is PEAR DB "a unified API for accessing SQL-databases." PEAR DB greatly exceeds the functionality of the DBX library and is almost purely object oriented. PEAR DB supports a decent subset of the core PHP-supported databases and is being extended to support even more. PEAR DB is a great tool to code database-independent PHP applications.

Downloading PEAR

You can download recent versions of PEAR from the PEAR Web site at pear.php.net. Type "DB" into the "search for" box in the upper right corner of the site.

Click on the first search result that comes up, "DB," then download the latest stable version from the list of releases.

Downloading PEAR from Concurrent Versions System (CVS)

Although PEAR is included with all recent versions of PHP and you can download later stable versions from the PEAR Web site, the latest and greatest version of PEAR with the latest features is probably still sitting in the CVS repository. Note that you should not use CVS versions on production Web sites! If you have access to CVS (www.cvshome.org), then you should take advantage of it and download the latest PEAR source code from the PHP CVS repository. You can find out all the specifics on the PHP CVS repository at http://cvs.php.net/.

To download the latest PEAR source:

  1. Change directory to the location that you want to place the source (or a convenient place from which you can copy the files).

  2. Execute the command: cvs -d :pserver:cvsread@cvs .php.net:/repository login

  3. You are prompted for a password. Enter "phpfi".

  4. Execute the command: cvs -d :pserver:cvsread@cvs .php.net:/repository export -D "last week" php4/pear

  5. Thomas V. V. Cox, one of the main contributors to the PEAR DB documentation, recommends using the "last week" flag. Sometimes the latest is a little buggy, but most bugs are fixed in a week.2

  6. Copy the pear folder over your existing pear folder in your PHP installation.

Installing PEAR

Once you have downloaded the source, you should modify your include_path setting in php.ini to point to the pear directory, or you could use the following function at the top of each script that requires access to PEAR:

ini_set("include_path", "path/to/pear"); 

Once you have the latest PEAR source, you are ready to begin. If you don't have the latest, you can still try out the examples, but your mileage may vary.

Back to the Basics

Now that you are ready to code a PEAR DB application, you have to learn the basics of connecting to and querying a database once again. Like any database-backed PHP application, you first have to connect to the database. PEAR DB uses the DB::connect() function for this purpose (notice the similarity to PERL's CPAN module syntax).

$dbconn = DB::connect(DSN);

DB::connect() takes one argument, a DSN. DSN stands for data source name, and it is a way to specify all the necessary settings needed to connect to the database in one neat package. A DSN is typically comprised of the following:

  • type—The type of database server to which you are connecting. See below for examples.

  • host—The host name of the database server to which you are connecting, optionally followed by the port.

  • database—The name of the database to which you are connecting.

  • username—The login of the user with access rights to the database.

  • password—The user's password.

The type of databases can be one of the following:

  • mysql—MySQL
  • pgsql—PostgreSQL
  • ibase—InterBase
  • msql—mSQL
  • mssql—Microsoft SQL Server
  • oci8—Oracle 7/8/8i
  • odbc—ODBC
  • sybase—Sybase
  • ifx—Informix
  • fbsql—FrontBase

All of this information is formatted in a single string:

$dsn = "type://username:password@host:port/database";

If your database doesn't require an option, such as the password, or if it is running on the standard port, then you can omit those from the DSN. If the connection is successful, then DB::connect() returns a valid connection object. If there was a failure, then it returns a DB Error object.

A PEAR DB-enabled page starts like this:

ini_set("include_path", "path/to/pear");
$type = "mssql";
$user = "mssqluser";
$pass = "password";
$host = "";
$database = "php";
$dsn = "$type://$user:$pass@$host/$database";
$dbconn = DB::connect($dsn);

Once you have attempted to make the connection, you should verify that it worked. PEAR DB provides the DB::isError() function to check if there was an error.


DB::isError() takes one argument, OBJECT, the object that was created by a previous PEAR DB function. In the example above, you would check for an error like this:

if (DB::isError($db)) { 
            die ($dbconn->getMessage());

Wait a second, it looks like something sneaked in there! $dbconn->getMessage() is a method that, when an error is produced, allows you to display any message associated with the error object. If the connection attempt doesn't work, the $dbconn turns into a DB Error object. If there is no error, then getMessage() won't work on $db, since it is a valid connection object.

Okay, so you've got a connection set up and a way to trap an error if the connection fails. The next thing you need to know how to do is send queries to your database. This is done using the query() method.

$result = $dbconn->query(QUERY);

query() takes one argument, QUERY, which is an SQL statement. You assign the result of that query to a variable, such as $result, which is a result object.

Once you have a valid result object, you can use one of the "fetch" methods to fetch the data from the result and then format and display it to the user or perform some other processing on it. There are two fetch methods that you can use: fetchRow() and fetchInto(). Both of these functions do essentially the same thing; however, their syntax is slightly different.

$row = $result->fetchRow();



produce exactly the same thing, a variable called $row that has the current row data from the result object.

You can specify the format of the data retrieved by the fetch methods by assigning an additional argument to the method. The fetch methods support three formats of data that they can retrieve. These are:

  • DB_FETCHMODE_ORDERED—(default) Data is formatted as an ordered array.

  • DB_FETCHMODE_ASSOC—Data is formatted as an associative array.

  • DB_FETCHMODE_OBJECT—Data is formatted as an object, with the column names as properties.

As an example, suppose you have the following information in a table (Table 3–2) called "crew":

TABLE 3–2 Sample Data



















You query the database and get a result:

$sql = "select name, origin from crew";
$result = $dbconn->query($slq);

The three formats would be:

//using the default format of DB_FETCHMODE_ORDERED
$row = $result->fetchRow();
$name = $row[0]; // $name = "Spike";
$origin = $row[1]; //$origin = "MA";

//using an associative array as the format
$row = $result->fetchRow(DB_FETCHMODE_ASSOC);
$name = $row['name']; // $name = "Spike";
$origin = $row['origin']; //$origin = "MA";

//using an object as the format
$result->fetchInto($row, DB_FETCHMODE_OBJECT);
$name = $row->name; // $name = "Spike";
$origin = $row->origin; //$origin = "MA";

These formats provide for a lot of flexibility. Also notice that the different fetch methods would produce the same expected result.

Since it can be a real drag having to type out DB_FETCHMODE_ASSOC or DB_FETCHMODE_OBJECT as an argument to every fetch method in your script (if you choose to use those formats), PEAR DB provides a nifty method called setFetchMode().


setFetchMode is a method for the connection object that sets the default fetch mode for all fetch functions. The argument, MODE, can be any one of the three fetch modes specified earlier. Note that it is pointless to set the fetch mode to DB_FETCHMODE_ORDERED if you haven't already set the fetch mode to one of the other values, since it is already the default. Once you use this method, all of the fetch methods that you call use the mode specified by setFetchMode(), unless you have specified a different fetch mode in the fetch method itself.

You should also check your results for errors using the same method as when checking the connection for errors. If a query() results in an error, then it returns an error object:

$result = $dbconn->query($sql);
if (DB::isError($result)) { die ($result->getMessage());} 

After you have finished with your result set, you should free the result object by using the free() method. This will "free" the memory associated with the result set and reduce the load on your Web server:


Finally, when you have completed your script, you should close the connection to the server. This is done using the disconnect method of the connection object:


You now have the building blocks to create a simple script. This next script illustrates the different fetch methods and errors.

Script 3–5 peardb1.php Script 3–6

  1.  <?
  2.  ini_set("include_path", "/path/to/php/pear");
  3.  require_once('DB.php');
  4.  $type = "mssql";
  5.  $user = "mssqluser";
  6.  $pass = "password";
  7.  $host = "";
  8.  $database = "php";
  9.  $dsn = "$type://$user:$pass@$host/$database";
10.  $dbconn = DB::connect($dsn);
11.  if (DB::isError($dbconn)) { die ($dbconn->getMessage()); }
12.  /*
13.  create table bebop (
14.          id INT,
15.          name VARCHAR(8),
16.          origin CHAR(2));
17.  */
18.  $values = array (
19.          "insert into bebop values ('0','Spike','MA')",
20.          "insert into bebop values ('1','Jett','AZ')",
21.          "insert into bebop values ('2','Faye','FL')",
22.          "insert into bebop values ('3','Ed','NM')",
23.          "insert into bebop values ('4','Ein','CO')"
24.          );
26.  $result = $dbconn->query("select * from bebop");
27.  if(DB::isError($result)) { die ($result->getMessage());}
28.  if($result->numRows() == 0) {
29.          echo "<P>Populating the DB!<p>";
30.          for($i = 0; $i < sizeof($values); $i++) {
31.              $result2 = $dbconn->query($values[$i]);
32.              if (DB::isError($result2)) { die ($result2->getMessage());}
33.          }
34.          echo "<P>Done the DB! Reload Page<p>";
35.  } else {
36.          $result = $dbconn->query("select name, origin from bebop");
37.          if (DB::isError($result)) { die ($result->getMessage());}
38.          echo "<P>Default Fetch Mode (DB_FETCHMODE_ORDERED):";
39.          while($result->fetchinto($row)){
40.              echo "<br>" . $row[0] . " " . $row[1];
41.          }
42.          $result = $dbconn->query("select name, origin from bebop");
43.          $dbconn->setFetchMode(DB_FETCHMODE_ASSOC);
44.          echo "<HR>DB_FETCHMODE_ASSOC Fetch Mode:";
45.          while($row = $result->fetchRow()){
46.              echo "<br>" . $row['name'] . " " . $row['origin'];
47.          }
48.          $result = $dbconn->query("select name, origin from bebop");
49.          $dbconn->setFetchMode(DB_FETCHMODE_OBJECT);
50.          echo "<HR>DB_FETCHMODE_OBJECT Fetch Mode:";
51.          while($result->fetchinto($row)){
52.          echo "<br>" . $row->name . " " . $row->origin;
53.          }
54.  }
55.  $result->free();
56.  $dbconn->disconnect();
57.  ?>

Script 3–5 peardb1.php Line-by-Line Explanation




Set the include path so that the PEAR library is accessible to your script.


Require the DB.php library from the PEAR distribution.


Define the require properties so that your script can connect to your database.


Build the DSN using the properties defined above.


Establish a connection to the database server.


If there is an error connecting to the database, then kill the script and display any message associated with the error.


Define the SQL statement needed to create the table used in this example.


Create an array of SQL statements that will be used to create entries in the database.


Query the database to see if anything exists in the table.


Check to see if the query from line 26 is an error. If it is, then kill the script and display the error message to the user.


If the number of rows returned in the result set is 0, then execute lines 29–34.


Notify the user that the script is populating the database.


Start a for loop to loop through the items in the $values array.


Execute a query for each of the items in the $value array.


If there is an error with the query, kill the script and display any error messages.


If no errors occur, notify users that the database has been populated and that they should reload the page.


If there are rows in the table (checked in line 28), then execute the rest of the script.


Query the database. If there is an error with the query, kill the script and display any error messages.


Display the results using DB_FETCHMODE_ORDERED. Note how the results are displayed on line 40.


Query the database.


Set the fetch mode.


Display the results using DB_FETCHMODE_ASSOC. Note how the results are displayed on line 46.


Query the database.


Set the fetch mode.


Display the results using DB_FETCHMODE_OBJECT. Note how the results are displayed on line 52.


End the if statement started on line 28.


Free the result.


Close the database connection.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020