PHP bindings for Xapian

The PHP bindings for Xapian are packaged in the xapian extension. The PHP API provided by this extension largely follows Xapian's C++ API. This document lists the differences and additions.

As of Xapian version 1.1.0, these bindings require PHP5 (PHP4 is no longer supported). With PHP 5.4, subclassing Xapian classes in PHP doesn't currently work properly (as demonstrated by "make check" failing with a segmentation fault). Apart from this everything seems to work fine with PHP 5.4, and all seems well with earlier PHP5 releases. It isn't yet clear if this is a bug in our interface files, the code SWIG generates, or in PHP 5.4.

PHP strings, arrays, etc., are converted automatically to and from the corresponding C++ types in the bindings, so generally you can pass arguments as you would expect. One thing to be aware of though is that SWIG implements dispatch functions for overloaded methods based on the types of the parameters, so you can't always pass in a string containing a number (e.g. "42") where a number is expected as you usually can in PHP. You need to explicitly convert to the type required - e.g. use (int) to convert to an integer, (string) to string, (double) to a floating point number.

With version 1.2.6 and later, you can subclass Xapian classes in PHP and virtual methods defined in PHP are called from C++ in the way you'd expect.

PHP has a lot of reserved words of various sorts, which sadly clash with common method names. Because of this empty() methods of various container-like classes are wrapped as is_empty() for PHP and the clone() method of the XapianWeight class and subclasses is wrapped as clone_object().

The examples subdirectory contains examples showing how to use the PHP bindings based on the simple examples from xapian-examples: simpleindex.php5, simplesearch.php5, simpleexpand.php5, simplematchdecider.php5.

Note that these examples are written to work with the command line (CLI) version of the PHP interpreter, not through a webserver. Xapian's PHP bindings may of course also be used under CGI, Apache's modphp, ISAPI, etc.

Installation

Assuming you have a suitable version of PHP installed, running configure will automatically enable the PHP bindings, and make install will install the extension shared library in the location reported by php-config --extension-dir.

Check that php.ini has a line like extension_dir = "<location reported by php-config --extension-dir>".

Then add this line to php.ini: extension = xapian.so (or whatever the library is called - not all UNIX systems use .so as the extension, and MS Windows uses .dll).

If you're using PHP as a webserver module (e.g. mod_php with Apache), you may need to restart the webserver for this change to take effect.

Alternatively, you can get scripts which use Xapian to explicitly load it. This approach is useful if you don't have root access and so can't make changes to php.ini. The simplest set up is to copy xapian.so into the same directory as your PHP script, and then add the following line to the start of your PHP scripts which use Xapian: dl('xapian.so');

You can put xapian.so elsewhere (and it's probably better to) but note that dl() requires a relative path so you might have to use something insane-looking like: dl('../../../../usr/lib/php5/20051025/xapian.so');

You also need to add include "xapian.php" to your PHP scripts which use Xapian in order to get the PHP class wrappers.

Exceptions

Exceptions thrown by Xapian are translated into PHP Exception objects which are thrown into the PHP script.

Object orientation

As of Xapian 0.9.7, the PHP bindings use a PHP object oriented style.

In order to construct an object, use $object = new XapianClassName(...);. Objects are destroyed when they go out of scope - to explicitly destroy an object you can use unset($object); or $object = Null;

You invoke a method on an object using $object->method_name().

Unicode Support

In Xapian 1.0.0 and later, the Xapian::Stem, Xapian::QueryParser, and Xapian::TermGenerator classes all assume text is in UTF-8. If you want to index strings in a different encoding, use the PHP iconv function to convert them to UTF-8 before passing them to Xapian, and when reading values back from Xapian.

Iterators

All iterators support next() and equals() methods to move through and test iterators (as for all language bindings). MSetIterator and ESetIterator also support prev().

In C++, trying to dereference or advance an iterator which is at its end point is undefined behaviour and should be avoided, and currently the PHP wrappers around the Xapian iterator classes inherit these semantics. The plan is to wrap these PHP iterators (see ticket#520).

Iterator dereferencing

C++ iterators are often dereferenced to get information, eg (*it). With PHP these are all mapped to named methods, as follows:

IteratorDereferencing method
PositionIterator get_termpos()
PostingIterator get_docid()
TermIterator get_term()
ValueIterator get_value()
MSetIterator get_docid()
ESetIterator get_term()

Other methods, such as MSetIterator::get_document(), are available unchanged.

MSet

MSet objects have some additional methods to simplify access (these work using the C++ array dereferencing):

Method nameExplanation
get_hit(index)returns MSetIterator at index
get_document_percentage(index)convert_to_percent(get_hit(index))
get_document(index)get_hit(index)->get_document()
get_docid(index)get_hit(index)->get_docid()

Database Factory Functions

Constants

Constants are wrapped as const members of the appropriate class. So Xapian::DB_CREATE_OR_OPEN is available as Xapian::DB_CREATE_OR_OPEN, Xapian::Query::OP_OR is available as XapianQuery::OP_OR, and so on.

Functions

Non-class functions are wrapped in the natural way, so the C++ function Xapian::version_string is wrapped under the same name in PHP.

Query

In C++ there's a Xapian::Query constructor which takes a query operator and start/end iterators specifying a number of terms or queries, plus an optional parameter. In PHP, this is wrapped to accept an array listing the terms and/or queries (you can specify a mixture of terms and queries if you wish) For example:

   $subq = new XapianQuery(XapianQuery::OP_AND, "hello", "world");
   $q = new XapianQuery(XapianQuery::OP_AND, array($subq, "foo", new XapianQuery("bar", 2)));

MatchAll and MatchNothing

In Xapian 1.3.0 and later, these are wrapped as static methods XapianQuery::MatchAll() and XapianQuery::MatchNothing().

If you want to be compatible with earlier versions, you can continue to use new XapianQuery('') for MatchAll and new XapianQuery() for MatchNothing.

Enquire

There is an additional method get_matching_terms() which takes an MSetIterator and returns a list of terms in the current query which match the document given by that iterator. You may find this more convenient than using the TermIterator directly.

Last updated $Date: 2013-01-09 10:45:40 +0000 (Wed, 09 Jan 2013) $