Simple databases for websites using SQLite with PHP5 and PDO
Click image to see working database display In a previous article, I described how SQLite could be used in HTML programs in VBScript with an ODBC driver. SQLite support is now part of PHP so I was keen to try SQLite with a simple database on one of my websites on a Linux server. You will find on the SQLite website (www.sqlite.org) a number of advantages to using SQLite. Here are some points that I thought were useful:- • No database server is needed; the whole database is in a single file which can be uploaded into your normal webspace. • The filesize is relatively small. I converted one small database from Access to SQLite with a reduction in filesize from 104 kb to 6 kb. • SQLite comes as part of the PHP5 package and PHP5 has good support for this database. Setting up the database There are several programs to help with setting up a SQLite database. Two freeware programs for Windows that I have tried and found very useful are SQLite Administrator and SQLite2007 Pro Enterprise Manager. Both allow conversion of a database from MS Access to SQLite. If your database is for display of data only and you are the only one who is updating the data, why not do all of your updating offline? The amendments can be made with one of these excellent programs and the amended file can be uploaded as you would any other file. It saves the time in developing a web interface for amendment. I see SQLite with PHP as particularly suited for simple databases, e.g. contact details of members or staff, where the expense of updating to a more expensive webhosting package with MySQL or SQL Server is not justifiable. This may be a little unfair to SQLite which can probably handle complicated databases very well, but I see its application to this kind of small database as a niche for which it is suited. The example shown here is not of member details as I did not want to use personal details. This article uses a database of classical music on a CD collection. All fields are simple text fields. DATABASE FIELDS Field Name Type Other Properties ID INTEGER PRIMARY KEY Composer TEXT Work TEXT Orchestra TEXT Conductor TEXT Soloist1 TEXT Instrument1 TEXT Soloist2 TEXT Instrument2 TEXT Soloist3 TEXT Instrument3 TEXT Recorded INTEGER
PHP I admire the ability of PHP to provide very concise code and I like the many useful functions. However, I struggle with the programming, especially with all that punctuation. It is the brackets in particular that give me trouble - ordinary brackets ( ), curly brackets { } and square brackets [ ]. You need good eyesight to spot the difference between an ordinary bracket ( ) and a curly bracket { }. As PHP has developed, even more punctuation has been introduced and we now have the double colon :: There seem to be three main approaches to using PHP5 with SQLite databases: 1. Using a set of specialised functions for interaction. These follow the pattern so successfully used with MySQL. 2. An object-orientated approach which begins with making an object of the database: $db = new SQLiteDatabase (cds.db3);
The brackets contain the path to the database. In this case, the database "cds.db3" is in the same directory as the program.
The database object then has a series of methods and properties which are based on the functions available in the first approach. 3. Using PDO. PDO stands for PHP Data Objects and is a unified interface for accessing databases in PHP. It requires that a PDO driver for a particular database be installed and can be seen as a PHP equivalent of the ODBC system in Windows. My webhosting company does not have a full implementation of PHP5 and so approaches 1 and 2 failed. It does have implementation of PDO and its SQLite Driver, so it was necessary to get familiar with this method. Programming with PDO We start by making an object of the database using the code: $db = new PDO('sqlite:cds.db3');
This is for a database "cds.db3" is in the same directory as the program. If it is not, use the relative path. We now need to get the recordset from the table, "discs". As this is not a big database we will get all records in one go, using the method "query" on the object $db. $result = $db->query('SELECT * FROM discs');
Beyond this, I initially ran into difficulties. I was looking for methods and properties that are a part of approaches 1 and 2 discussed above; they are not there and you are left to work things out for yourself. I particularly wanted a generic display that would retrieve the field names, but had problems finding a method that would give these. After rereading the documentation on the www.php.net website, the penny dropped. PDO has a number of FETCH methods and, of these, two seemed particularly useful: $row = $result->fetch(PDO::FETCH_ASSOC); $rowarray = $result->fetchall(PDO::FETCH_ASSOC);
The first will return an array of the next row in the recordset. Note the double colon. The attribute FETCH_ASSOC means that the array returned is indexed by field name. Other attributes are available to retrieve other kinds of arrays from the recordset, but this is particularly suited as it enables the field names to be recalled. The second method ('fetchall') retrieves all rows and is an array of arrays. We will use this as our database is relatively small and then we can use array procedures to get the data. Populating the dropdown box We will use a dropdown menu like this to select records:- Qui è inserito un pulsante a discesa che permette di scegliere tra le chiavi che saranno utilizzate per popolare il database (ex. tra Beethoven Violin Concert in D Major; Brahms Violin Concert in D Major; Finzi Clarinet Concerto) The menu will be populated by key information from the database, in this case the composer and the work. Frequently, you find a button to the right of the menu to activate the selection. However, it is simpler if you can just click on the option to activate the process of finding the record. This we can do if we use the event onChange which activates the submission of the form using Javscript and recalls the same file.
To populate the dropdown menu, we get the complete set of results, as shown above, in the array of arrays $rowarray. This array is then parsed as its constituent row arrays ($row) using a foreach loop. A counter, $rowno, is used to assign a value to the options in the menu. The values for the fields, Composer and Work, are displayed in the dropdown menu. Displaying the record The record will be displayed as a table of field names in the first column and the values in the second column. This is a generic routine which does not require prior knowledge of the field names. The headings are not generic and display the composer and the work.
$row = $rowarray[$rowno]; echo "
$row[Composer]
"; echo "$row[Work]
"; echo "| $key | $val | echo "
First, it should be established whether a submission has taken place. If there has, there will be a value for $_GET[rowno] and we give its value to $rowno. If there was no submission, the value of $rowno is set to 0 in order to display the first record in the database. The chosen record in the recordset is retrieved as $rowarray[$rowno]. The headings for Composer and Work are displayed and then the table is generated using a foreach loop to display key/value pairs retrieved from the record, $row. Conclusion You can see this database working here. If you are intending using this approach on a website, check with the information from your webhosting company on the requirements for PHP5. My former web host required the file to end with the suffix ".php5" for PHP5 to be invoked. This will not work with the current host;".php" suffices. This article has shown how it is possible to use SQLite for a simple web database and to control display and retrieval of records using PHP5 with PDO. The database can simply be uploaded as a normal file and is compact (in this case, 6.1 kB with the display program of only 2.6 kB). The program shown offers record retrieval through a dropdown menu and a display of the record as a table. The basics shown here can be expanded to provide customised solutions for other purposes. References • SQLite, Chapter 4 in "Upgrading to PHP5", Adam Trachtenberg, O'Reilly. Chapter available free online. • SQLite Functions, PHP Documentation • PDO Functions, PHP Documentation • SQLite Tutorial - SQLite with PHP 5 / SQL, LiteWebsite • Introduction to Using SQLite with PHP 5, Alejandro Gervasio • Using Unbuffered Queries and More with SQLite with PHP 5, Alejandro Gervasio • Additional Methods for Using SQLite with PHP 5, Alejandro Gervasio Adding navigation buttons to a simple web SQLite database •
Click image to see working database display
This builds on the database developed in a previous article. This described how SQLite and PHP5 with PDO could be used to produce a simple web database. Now we are going to add navigation buttons to allow the user to select the First, Previous, Next and Last record. The navigation buttons The four navigation buttons are added within the control form at the top of the display page underneath the dropdown box. All are of the type "submit" and, as defined in the original code, will cause the reloading of the same file with the action "GET". All have the name "navigate" and we will use this to test after submission whether a navigation button has been pressed or the dropdown menu has been selected.
Amendments to code We need to make two amendments to the code to give us more information: • The total number of records to establish the last record. We already have a count of the number of rows so that we can use this to give a value for the last row. $rowno = 0; foreach($rowarray as $row) { echo ""; $rowno++; }
$lastrow=$rowno - 1; $rowno = 0;
• The row number of the current record needs to be sent when submitted. From this we can establish what is the next or previous record. This is sent through a hidden field on the form.
Acting on the control used for submission The get method could return up to three parameters depending on which control is used for submission:- 1. "navigate" if one of the navigation buttons is pressed 2. "rowno" if the dropdown menu is used. 3. "currentrow" if either is used. if ($_GET[navigate]) { switch ($_GET[navigate]) { case "First": $rowno = 0; break; case "Prev": if ($_GET[currentrow]!= 0) {$rowno = $_GET[currentrow] - 1;} else {$rowno = 0;} break; case "Next": if ($_GET[currentrow]!= $lastrow) {$rowno = $_GET[currentrow] + 1;} else {$rowno = $lastrow;} break; case "Last": $rowno = $lastrow;
break; } }
First we test whether a navigation button has been pressed by seeing whether there is a value for $_GET[navigate]. If there is, a switch routine choses the action based on its value. First and Last are straightforward with $rowno being equal to 0 or $lastrow, respectively. For Prev and Next, we need to make sure we do not go off the ends. For Prev, if the value of $_GET[currentrow] is not 0, we make $rowno equal to $_GET[currentrow] - 1. If it is 0, we keep $rowno as 0. For Next, we test to see whether $_GET[currentrow] is not equal to $lastrow. If so, we increment the row number by 1, otherwise the rownumber is kept at the value for $lastrow. Then we test whether the dropdown menu was used for submission, in which case there will be a value for $_GET[rowno] and we set $rowno to the value of $_GET[rowno]. The last possibility is that there was no submission at all, i.e. the page is first loaded. In this case, $rowno is set to 0 so that the first record is displayed. elseif ($_GET[rowno]) { $rowno = $_GET[rowno];} else {$rowno = 0;} Conclusion In VBScript with OBDC, we can navigate the recordset with the methods movefirst, moveprevious, movenext and movelast. With SQlite, PDO and PHP, we do not have these functions, but, as this article shows, it is not difficult to devise your own code to carry out these functions. You can see this further development of the database working here. If you are intending using this approach on a website, check with the information from your webhosting company on the requirements for PHP5. Mine requires the file to end with the suffix ".php5" for PHP5 to be invoked.