IS2803 Developing Multimedia Applications for Business (Part 2) Lecture 6: Accessing a database with PHP Rob Gleasure robgleasure.com

IS2803 Today's lecture  Accessing a database with PHP  An example

Accessing Databases with SQL As we saw in lecture 4, accessing files in PHP requires a number of steps and databases are no different. These steps (roughly) are:  Open a connection with the file  Read data from the file into a file handle variable  Manipulate the contents of the file (optional)  Close the connection

Accessing Databases with SQL Imagine the following database table leaders in politicians.accdb IDFirstnameSurname 1EndaKenny 2EamonGilmore 3MichealMartin 4GerryAdams

Accessing Databases with SQL To connect to MS Access we use the COM() function  This function creates an instance of the ActiveX Data Object (ADO), which is part of the component object model (COM) object for accessing databases and other similar data sources <?php //create an instance of the ADO connection object $conn = new COM('ADODB.Connection') or die('Cannot start ADO'); ?> Note that, just as when we were opening files in lecture 4, we are saving the connection details in a file handle (In this case ‘$conn’)

Accessing Databases with SQL Next we create a connection string to hold the database driver details and the absolute URL of the database //in this example the URL for our database is ‘C:/myFolder/politicians.accdb’ $connStr = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source= C:/ myFolder/politicians.accdb;Persist Security Info=False;"; Note that if we’re using the old MS Access format (.mdb), our connection string will look a little different $connStr = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source=C:/xampp/htdocs/politicians.mdb"; However,.mdb issues shouldn't be a concern for us in this course

Reading from a database Next, we pass the connection string variable (in this case $connStr) to the open function //Open the connection to the database $conn->open($connStr); Again, note that we are saving all the connection details in the file handle ‘$conn’

Reading from a database Similar to the process for reading text files from lecture 4, we need to read the contents of a database into a variable When a variable is allocated the output from a SELECT query, this variable now stores what is called a ‘record set’ To run the SELECT query (or any other SQL queries) we call the ADO function ->execute() on the record set variable //Code to create a variable $rS to store a new record set from your table $rS = $conn->execute("SELECT * FROM leaders");

Reading from a database We can now pull information out of the record set variable using the ->Fields() function. $id= $rS->Fields(0); $firstname= $rS->Fields(1); $surname = $rS->Fields(2); Note that ->Fields() works on a single record in the Recordset object (i.e. one row in the table)

Reading from a database We spoke last week about pointers. ADO comes with a number of built-in functions (we have already seen open() and execute()) and a couple of these are especially important for moving a pointer (i.e. navigating) around a record set  MoveFirst (): moves to the first record in a Recordset object  MoveLast(): moves to the last record in a Recordset object  MoveNext(): moves to the next record in a Recordset object  MovePrevious(): moves to the previous record in a Recordset object Note: errors will be thrown if these functions are called and the pointer has nowhere to go, e.g. if database is empty or EOF has been reached

Reading from a database We can use these functions to iterate through the records stored in the record set while (!$rS->EOF) //while $rS is not at end of file { echo "First name is ".$rS->Fields(1)." "; // we then move to next record $rS->MoveNext(); }

Writing to a database Writing to a database is very similar, the difference is in our SQL statement //Code to execute sql statement to insert name John into leaders field FirstName $conn->execute("INSERT INTO leaders (FirstName) VALUES (6, 'Joan‘,’Collins’)"); Each time this statement runs, it will try to insert this data into a new row in the table

Closing the connection As with all files, when we’re finished we must ensure we close the connection. This closing requires two steps with databases //release memory from rS $rS->Close(); //release memory from conn $conn->Close();

An example Try out the following code Lecture 6 example <?php /**/ // create an instance of the ADO connection object $conn = new COM ("ADODB.Connection") or die("Cannot start ADO"); // define connection string, specify database driver $connStr = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:/xampp2/htdocs/IS2803.accdb;Persist Security Info=False;"; // open the connection to the database $conn->open($connStr); // create a variable to store a SQL query that selects every field where the Username is the same as $username $myQuery = "SELECT * FROM Politicians"; // create a variable $rS to store the new record returned when the SQL query is executed $rS = $conn->execute($myQuery); echo ' '; echo ' First name Surname '; echo ' '; while (!$rS->EOF){ // echo out the details from one record at a time echo ' '; echo ' '.$rS->Fields(1).' '.$rS->Fields(1).' '; echo ' '; // then move to next record $rS->MoveNext(); } echo ' '; $rS->close(); $conn->close(); ?>

Troubleshooting You may get an error that reads “Fatal error: Class 'COM' not found…” This occurs because a previously default driver isn’t default any more The solution is to open xampp/php/php.ini and add the following lines to the end [PHP_COM_DOTNET] extension=php_com_dotnet.dll

Want to read more? Links and references  W3Schools tutorial on PHP and MS Access  Generic tutorial on PHP and SQL connections Tutorial-P843.html Tutorial-P843.html