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Natively Connect to Cassandra Data in PHP

The CData ODBC Driver for Cassandra enables you to create PHP applications on Linux/UNIX machines with connectivity to Cassandra data. Leverage the native support for ODBC in PHP.

Drop the CData ODBC Driver for Cassandra into your LAMP or WAMP stack to build Cassandra-connected Web applications. This article shows how to use PHP's ODBC built-in functions to connect to Cassandra data, execute queries, and output the results.

Using the CData ODBC Drivers on a UNIX/Linux Machine

The CData ODBC Drivers are supported in various Red Hat-based and Debian-based systems, including Ubuntu, Debian, RHEL, CentOS, and Fedora. There are also several libraries and packages that are required, many of which may be installed by default, depending on your system. For more information on the supported versions of Linux operating systems and the required libraries, please refer to the "Getting Started" section in the help documentation (installed and found online).

Installing the Driver Manager

Before installing the driver, check that your system has a driver manager. For this article, you will use unixODBC, a free and open source ODBC driver manager that is widely supported.

For Debian-based systems like Ubuntu, you can install unixODBC with the APT package manager:

$ sudo apt-get install unixODBC unixODBC-dev

For systems based on Red Hat Linux, you can install unixODBC with yum or dnf:

$ sudo yum install unixODBC unixODBC-devel

The unixODBC driver manager reads information about drivers from an odbcinst.ini file and about data sources from an odbc.ini file. You can determine the location of the configuration files on your system by entering the following command into a terminal:

$ odbcinst -j

The output of the command will display the locations of the configuration files for ODBC data sources and registered ODBC drivers. User data sources can only be accessed by the user account whose home folder the odbc.ini is located in. System data sources can be accessed by all users. Below is an example of the output of this command:

DRIVERS............: /etc/odbcinst.ini SYSTEM DATA SOURCES: /etc/odbc.ini FILE DATA SOURCES..: /etc/ODBCDataSources USER DATA SOURCES..: /home/myuser/.odbc.ini SQLULEN Size.......: 8 SQLLEN Size........: 8 SQLSETPOSIROW Size.: 8

Installing the Driver

You can download the driver in standard package formats: the Debian .deb package format or the .rpm file format. Once you have downloaded the file, you can install the driver from the terminal.

The driver installer registers the driver with unixODBC and creates a system DSN, which can be used later in any tools or applications that support ODBC connectivity.

For Debian-based systems like Ubuntu, run the following command with sudo or as root: $ dpkg -i /path/to/package.deb

For Red Hat systems or other systems that support .rpms, run the following command with sudo or as root: $ rpm -i /path/to/package.rpm

Once the driver is installed, you can list the registered drivers and defined data sources using the unixODBC driver manager:

List the Registered Driver(s)

$ odbcinst -q -d CData ODBC Driver for Cassandra ...

List the Defined Data Source(s)

$ odbcinst -q -s CData Cassandra Source ...

To use the CData ODBC Driver for Cassandra with unixODBC, ensure that the driver is configured to use UTF-16. To do so, edit the INI file for the driver (cdata.odbc.cassandra.ini), which can be found in the lib folder in the installation location (typically /opt/cdata/cdata-odbc-driver-for-cassandra), as follows:

cdata.odbc.cassandra.ini

... [Driver] DriverManagerEncoding = UTF-16

Modifying the DSN

The driver installation predefines a system DSN. You can modify the DSN by editing the system data sources file (/etc/odbc.ini) and defining the required connection properties. Additionally, you can create user-specific DSNs that will not require root access to modify in $HOME/.odbc.ini.

Set the Server, Port, and Database connection properties to connect to Cassandra. Additionally, to use internal authentication set the User and Password connection properties.

/etc/odbc.ini or $HOME/.odbc.ini

[CData Cassandra Source] Driver = CData ODBC Driver for Cassandra Description = My Description Database = MyCassandraDB Port = 7000 Server = 127.0.0.1

For specific information on using these configuration files, please refer to the help documentation (installed and found online).

Establish a Connection

Open the connection to Cassandra by calling the odbc_connect or odbc_pconnect methods. To close connections, use odbc_close or odbc_close_all.

$conn = odbc_connect("CData ODBC Cassandra Source","user","password");

Connections opened with odbc_connect are closed when the script ends. Connections opened with the odbc_pconnect method are still open after the script ends. This enables other scripts to share that connection when they connect with the same credentials. By sharing connections among your scripts, you can save system resources and queries execute faster.

$conn = odbc_pconnect("CData ODBC Cassandra Source","user","password"); ... odbc_close($conn); //persistent connection must be closed explicitly

Create Prepared Statements

Create prepared statements and parameterized queries with the odbc_prepare function.

$query = odbc_prepare($conn, "SELECT * FROM Customer WHERE FirstName = ?");

Execute Queries

Execute prepared statements with odbc_execute.

$conn = odbc_connect("CData ODBC Cassandra Source","user","password"); $query = odbc_prepare($conn, "SELECT * FROM Customer WHERE FirstName = ?"); $success = odbc_execute($query, array('Bob'));

Execute nonparameterized queries with odbc_exec.

$conn = odbc_connect("CData ODBC Cassandra Source","user","password"); $query = odbc_exec($conn, "SELECT City, SUM(TotalDue) FROM Customer GROUP BY City");

Process Results

Access a row in the result set as an array with the odbc_fetch_array function.

$conn = odbc_connect("CData ODBC Cassandra data Source","user","password"); $query = odbc_exec($conn, "SELECT City, SUM(TotalDue) FROM Customer GROUP BY City"); while($row = odbc_fetch_array($query)){ echo $row["City"] . "\n"; }

Display the result set in an HTML table with the odbc_result_all function.

$conn = odbc_connect("CData ODBC Cassandra data Source","user","password"); $query = odbc_prepare($conn, "SELECT * FROM Customer WHERE FirstName = ?"); $success = odbc_execute($query, array('Bob')); if($success) odbc_result_all($query);

More Example Queries

You will find complete information on the SQL queries supported by the driver in the help documentation. The code examples above are Cassandra-specific adaptations of the PHP community documentation for all ODBC functions.