This extension offers a PHP interface to the YAZ toolkit that implements the Z39.50 Protocol for Information Retrieval. With this extension you can easily implement a Z39.50 origin (client) that searches or scans Z39.50 targets (servers) in parallel.
The module hides most of the complexity of Z39.50 so it should be fairly easy to use. It supports persistent stateless connections very similar to those offered by the various RDB APIs that are available for PHP. This means that sessions are stateless but shared among users, thus saving the connect and initialize phase steps in most cases.
Note: This extension has been moved to the PECL repository and is no longer bundled with PHP as of PHP 5.0.0.
Obtain YAZ (ANSI/NISO Z39.50 support) and install it. YAZ can be fetched in source or in various prebuilt packages from the YAZ archive. Systems such as Debian GNU/Linux, Suse Linux, FreeBSD also has YAZ as part of their distribution.
For the PHP 4 series, the YAZ extension is bundled (but not YAZ itself) Build PHP with your favorite modules and add option --with-yaz[=DIR].
For PHP 5, the YAZ extension is in PECL and is installed as a shared object/dll. If you have pear installed the easiest way to download, configure and install the YAZ extension is by using the pear command.
On Windows, php_yaz.dll depend on yaz.dll. The yaz.dll is part of the Win32 ZIP from the PHP site. It is also part of the Windows YAZ install available from the YAZ WIN32 area.
The PHP 5.0.5 Win32 zip includes a too old version of yaz.dll (version 1.9.1 < required version 2.0.13). If that's the case use the yaz.dll from a newer YAZ WIN32 install.
On windows, don't forget to add the PHP directory to the PATH, so that the yaz.dll file can be found by the system.
If you are using YAZ as a shared extension, add (or uncomment) the following line in php.ini on Unix:
Note: The above problem is solved in version 2.0 of YAZ.
The behaviour of these functions is affected by settings in php.ini.
Table 1. YAZ configuration options
|yaz.max_links||"100"||PHP_INI_ALL||Available since PHP 4.3.0.|
|yaz.log_file||NULL||PHP_INI_ALL||Available since PHP 4.3.0.|
This extension has no resource types defined.
This extension has no constants defined.
PHP/YAZ keeps track of connections with targets (Z-Associations). A resource represents a connection to a target.
The script below demonstrates the parallel searching feature of the API. When invoked with no arguments it prints a query form; else (arguments are supplied) it searches the targets as given in array host.
Example 3. Parallel searching using Yaz