Home > Articles > Data > MySQL

Using Arrays in PHP

This chapter is from the book

Multidimensional Arrays

Arrays do not have to be a simple list of keys and values—each location in the array can hold another array. This way, we can create a two-dimensional array. You can think of a two dimensional array as a matrix, or grid, with width and height or rows and columns.

If we want to store more than one piece of data about each of Bob's products, we could use a two-dimensional array.

Figure 3.3 shows Bob's products represented as a two-dimensional array with each row representing an individual product and each column representing a stored product attribute.

Figure 3.3Figure 3.3 We can store more information about Bob's products in a two- dimensional array.

Using PHP, we would write the following code to set up the data in the array shown in Figure 3.3.

$products = array( array( 'TIR', 'Tires', 100 ),
          array( 'OIL', 'Oil', 10 ),
          array( 'SPK', 'Spark Plugs', 4 ) );

You can see from this definition that our products array now contains three arrays.

To access the data in a one-dimensional array, recall that we need the name of the array and the index of the element. A two-dimensional array is similar, except that each element has two indices—a row and a column. (The top row is row 0 and the far left column is column 0.)

To display the contents of this array, we could manually access each element in order like this:

echo '|'.$products[0][0].'|'.$products[0][1].'|'.$products[0][2].'|<br />';
echo '|'.$products[1][0].'|'.$products[1][1].'|'.$products[1][2].'|<br />';
echo '|'.$products[2][0].'|'.$products[2][1].'|'.$products[2][2].'|<br />';

Alternatively, we could place a for loop inside another for loop to achieve the same result.

for ( $row = 0; $row < 3; $row++ )
{
 for ( $column = 0; $column < 3; $column++ )
 {
  echo '|'.$products[$row][$column];
 }
 echo '|<br />';
}

Both versions of this code produce the same output in the browser:

|TIR|Tires      |100|
|OIL|Oil        |10 |
|SPK|Spark Plugs|4  |

The only difference between the two examples is that your code will be shorter if you use the second version with a large array.

You might prefer to create column names instead of numbers as shown in Figure 3.3. To do this, you can use associative arrays. To store the same set of products, with the columns named as they are in Figure 3.3, you would use the following code:

$products = array( array( Code => 'TIR', 
             Description => 'Tires', 
             Price => 100 
            ),
          array( Code => 'OIL', 
             Description => 'Oil', 
             Price => 10 
            ),
          array( Code => 'SPK', 
             Description => 'Spark Plugs', 
             Price =>4 
            ) 
         );

This array is easier to work with if you want to retrieve a single value. It is easier to remember that the description is stored in the Description column than to remember that it is stored in column 1. Using associative arrays, you do not need to remember that an item is stored at [x][y]. You can easily find your data by referring to a location with meaningful row and column names.

We do however lose the ability to use a simple for loop to step through each column in turn. Here is one way to write code to display this array:

for ( $row = 0; $row < 3; $row++ )
{
 echo '|'.$products[$row]['Code'].'|'.$products[$row]['Description'].
    '|'.$products[$row]['Price'].'|<br />';
}

Using a for loop, we can step through the outer, numerically indexed $products array. Each row in our $products array is an associative array. Using the each() and list() functions in a while loop, we can step through the associative arrays. Therefore, we need a while loop inside a for loop.

for ( $row = 0; $row < 3; $row++ )
{
 while ( list( $key, $value ) = each( $products[ $row ] ) )
 {
  echo "|$value";
 }
 echo '|<br />';
}

We do not need to stop at two dimensions—in the same way that array elements can hold new arrays, those new arrays in turn can hold more arrays.

A three-dimensional array has height, width, and depth. If you are comfortable thinking of a two-dimensional array as a table with rows and columns, imagine a pile or deck of those tables. Each element will be referenced by its layer, row, and column.

If Bob divided his products into categories, we could use a three-dimensional array to store them. Figure 3.4 shows Bob's products in a three-dimensional array.

Figure 3.4Figure 3.4 This three-dimensional array allows us to divide products into categories.

From the code that defines this array, you can see that a three-dimensional array is an array containing arrays of arrays.

$categories = array( array ( array( 'CAR_TIR', 'Tires', 100 ),
               array( 'CAR_OIL', 'Oil', 10 ),
               array( 'CAR_SPK', 'Spark Plugs', 4 )
              ),
           array ( array( 'VAN_TIR', 'Tires', 120 ),
               array( 'VAN_OIL', 'Oil', 12 ),
               array( 'VAN_SPK', 'Spark Plugs', 5 )
              ),
           array ( array( 'TRK_TIR', 'Tires', 150 ),
               array( 'TRK_OIL', 'Oil', 15 ),
               array( 'TRK_SPK', 'Spark Plugs', 6 )
              )
          );

Because this array has only numeric indices, we can use nested for loops to display its contents.

for ( $layer = 0; $layer < 3; $layer++ )
{
 echo "Layer $layer<br />";
 for ( $row = 0; $row < 3; $row++ )
 {
  for ( $column = 0; $column < 3; $column++ )
  {
   echo '|'.$categories[$layer][$row][$column];
  }
  echo '|<br />';
 }
}

Because of the way multidimensional arrays are created, we could create four-, five-, or six-dimensional arrays. There is no language limit to the number of dimensions, but it is difficult for people to visualize constructs with more than three dimensions. Most real-world problems match logically with constructs of three or fewer dimensions.

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.

Overview


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.

Surveys

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.

Newsletters

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.

Security


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

Children


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

Marketing


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.

Choice/Opt-out


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.

Links


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