Home > Articles > Programming > PHP

This chapter is from the book

Accessing Information

Now that we can add information to a database, we need to look at strategies for retrieving the information that it contains. As you might guess, you can use mysql_query() to make a SELECT query. How do you use this to look at the returned rows, though? When you perform a successful SELECT query, mysql_query() returns a result resource. You can pass this resource to other functions to access and gain information about a result set.

Finding the Number of Rows Found by a Query

You can find the number of rows returned as a result of a SELECT query using the mysql_num_rows() function. mysql_num_rows() requires a result resource and returns a count of the rows in the set. Listing 12.4 uses a SQL SELECT statement to request all rows in the domains table and then uses mysql_num_rows() to determine the table's size. If all we wanted to do was to find the number of rows in the table then the approach in listing 12.4 would be very wasteful. We would do better to use MySQL's COUNT function. Imagine however, that we intend to work with the rows we have found in any case. Perhaps we wish to write the contents of the table to the browser. Having used SELECT for this purpose, we can use mysql_num_rows() to find some useful summary information about the request.

Listing 12.4 Finding the Number of Rows Returned by a SELECT Statement with mysql_num_rows()

 1: <html>
 2: <head>
 3: <title>Listing 12.4 Using mysql_num_rows()</title>
 4: </head>
 5: <body>
 6: <?php
 7: $user = "harry";
 8: $pass = "elbomonkey";
 9: $db = "sample";
10: $link = mysql_connect( "localhost", $user, $pass );
11: if ( ! $link )
12:   die( "Couldn't connect to MySQL" );
13: mysql_select_db( $db, $link ) 
14:   or die ( "Couldn't open $db: ".mysql_error() );
15: $result = mysql_query( "SELECT * FROM domains" );
16: $num_rows = mysql_num_rows( $result );
17: print "There are currently $num_rows rows in the table<P>";
18: //
19: // Further work with the $result resource here
20: //
21: mysql_close( $link );
22: ?>
23: </body>
24: </html> 

The mysql_query() function returns a result resource. We then pass this to mysql_num_ rows(), which returns the total number of rows found.

We connect to the database on line 10 and select the database on line 13. On line 15 we call mysql_query(), passing it our SQL query. The function returns a result resource that we can then use with mysql_num_rows() on line 16. Having output summary information on line 17 we are ready to begin to do some more substantial work with our results. We go on to do this in the next section.

Accessing a Resultset

After you have performed a SELECT query and gained a result resource, you can use a loop to access each found row in turn. PHP maintains an internal pointer that keeps a record of your position within a found set. This moves on to the next row as each one is accessed.

You can easily get an array of the fields in each found row with mysql_fetch_row(). This function requires a result resource, returning an array containing each field in the row. When the end of the found set is reached, mysql_fetch_row() returns false. Listing 12.5 outputs the entire domains table to the browser.

Listing 12.5 Listing All Rows and Fields in a Table

 1: <html>
 2: <head>
 3: <title>Listing 12.5 Listing all rows and fields in a table</title>
 4: </head>
 5: <body>
 6: <?php
 7: $user = "harry";
 8: $pass = "elbomonkey";
 9: $db = "sample";
10: $link = mysql_connect( "localhost", $user, $pass );
11: if ( ! $link )
12:   die( "Couldn't connect to MySQL" );
13: mysql_select_db( $db, $link ) 
14:   or die ( "Couldn't open $db: ".mysql_error() );
15: $result = mysql_query( "SELECT * FROM domains" );
16: $num_rows = mysql_num_rows( $result );
17: print "There are currently $num_rows rows in the table<P>";
18: print "<table border=1>\n";
19: while ( $a_row = mysql_fetch_row( $result ) ) {
20:   print "<tr>\n";
21:   foreach ( $a_row as $field )
22:     print "\t<td>$field</td>\n";
23:   print "</tr>\n";
24: }
25: print "</table>\n";
26: mysql_close( $link );
27: ?>
28: </body>
29: </html>

After we have connected to the server and selected the database, we use mysql_query() on line 15 to send a SELECT statement to the database server. We store the returned result resource in a variable called $result. We use this to acquire the number of found rows as before.

In the test expression of our while statement on line 19, we assign the result of mysql_ fetch_row() to the variable $a_row. Remember that an assignment operator returns the value of its right-hand operand, so the assignment resolves to true as long as mysql_ fetch_row() returns a positive value. Within the body of the while statement, we loop through the row array contained in $a_row on line 21, outputting each element to the browser embedded in a table cell.

You can also access fields by name in one of two ways. mysql_fetch_array() returns a numeric array, as does mysql_fetch_row(). It also returns an associative array, with the names of the fields as the keys. The following fragment rewrites the while statement from Listing 12.5, incorporating mysql_fetch_array() (this replaces lines 18 to 25):

print "<TABLE BORDER=1>\n";
while ( $a_row = mysql_fetch_array( $result ) ) {
  print "<TR>\n";
  print "<TD>".$a_row['mail']."</TD><TD>".$a_row['domain']."</TD>\n";
  print "</TR>\n";
print "</TABLE>\n";

The default behavior of mysql_fetch_array() is to return an array indexed by string which also contains the same values indexed numerically. This is fine if you want to refer to your fields individually. If, however you need to dump all the array values and keys, you will not want this duplication. mysql_fetch_array() accepts an optional second argument. This integer should be one of three built-in constants. MYSQL_ASSOC, MYSQL_NUM, or MYSQL_BOTH. Passing MYSQL_BOTH is redundant in that it will enforce the default behavior. Passing MYSQL_ASSOC to mysql_fetch_array() will ensure that the return array is indexed by strings only. Passing MYSQL_NUM to mysql_fetch_array() will ensure that the return array is numerically indexed.

If you are seeking the functionality provided by

mysql_fetch_array( $result, MYSQL_ASSOC );

you can use a shortcut function which was introduced with PHP 4.03. mysql_fetch_ assoc() is functionally identical to a call to mysql_fetch_array() with MYSQL_ASSOC.

You can also extract the fields from a row as properties of an object with mysql_fetch_ object(). The field names become the names of the properties. The following fragment once again rewrites the while statement from Listing 12.5, this time incorporating mysql_fetch_object() (this replaces lines 18 to 25):

print "<table border=1>\n";
while ( $a_row = mysql_fetch_object( $result ) ) {
  print "<tr>\n";
  print "<td>$a_row->mail</td><td>$a_row->domain</td>\n";
  print "</tr>\n";
print "</table>\n";

Both mysql_fetch_array() and mysql_fetch_object() make it easier for you to selectively extract information from a row. Neither of these functions takes much longer than mysql_fetch_row() to execute. Which you choose to use is largely a matter of preference, although mysql_fetch_array() is more commonly used.

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