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Zend Framework 2 Documentation (Manual) | |
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File: /_sources/modules/zendsearch.lucene.charset.txt
Size: | 4844 |
Storage flags: | no_autoload,compress/gzip (38%) |
.. _zendsearch.lucene.charset:
Character Set
=============
.. _zendsearch.lucene.charset.description:
UTF-8 and single-byte character set support
-------------------------------------------
``Zend\Search\Lucene`` works with the UTF-8 charset internally. Index files store unicode data in Java's "modified
UTF-8 encoding". ``Zend\Search\Lucene`` core completely supports this encoding with one exception. [#]_
Actual input data encoding may be specified through ``Zend\Search\Lucene`` *API*. Data will be automatically
converted into UTF-8 encoding.
.. _zendsearch.lucene.charset.default_analyzer:
Default text analyzer
---------------------
However, the default text analyzer (which is also used within query parser) uses ctype_alpha() for tokenizing text
and queries.
ctype_alpha() is not UTF-8 compatible, so the analyzer converts text to 'ASCII//TRANSLIT' encoding before indexing.
The same processing is transparently performed during query parsing. [#]_
.. note::
Default analyzer doesn't treats numbers as parts of terms. Use corresponding 'Num' analyzer if you don't want
words to be broken by numbers.
.. _zendsearch.lucene.charset.utf_analyzer:
UTF-8 compatible text analyzers
-------------------------------
``Zend\Search\Lucene`` also contains a set of UTF-8 compatible analyzers:
``Zend\Search\Lucene\Analysis\Analyzer\Common\Utf8``, ``Zend\Search\Lucene\Analysis\Analyzer\Common\Utf8Num``,
``Zend\Search\Lucene\Analysis\Analyzer\Common\Utf8\CaseInsensitive``,
``Zend\Search\Lucene\Analysis\Analyzer\Common\Utf8Num\CaseInsensitive``.
Any of this analyzers can be enabled with the code like this:
.. code-block:: php
:linenos:
Zend\Search\Lucene\Analysis\Analyzer::setDefault(
new Zend\Search\Lucene\Analysis\Analyzer\Common\Utf8());
.. warning::
UTF-8 compatible analyzers were improved in Zend Framework 1.5. Early versions of analyzers assumed all
non-ascii characters are letters. New analyzers implementation has more accurate behavior.
This may need you to re-build index to have data and search queries tokenized in the same way, otherwise search
engine may return wrong result sets.
All of these analyzers need PCRE (Perl-compatible regular expressions) library to be compiled with UTF-8 support
turned on. PCRE UTF-8 support is turned on for the PCRE library sources bundled with *PHP* source code
distribution, but if shared library is used instead of bundled with *PHP* sources, then UTF-8 support state may
depend on you operating system.
Use the following code to check, if PCRE UTF-8 support is enabled:
.. code-block:: php
:linenos:
if (@preg_match('/\pL/u', 'a') == 1) {
echo "PCRE unicode support is turned on.\n";
} else {
echo "PCRE unicode support is turned off.\n";
}
Case insensitive versions of UTF-8 compatible analyzers also need `mbstring`_ extension to be enabled.
If you don't want mbstring extension to be turned on, but need case insensitive search, you may use the following
approach: normalize source data before indexing and query string before searching by converting them to lowercase:
.. code-block:: php
:linenos:
// Indexing
setlocale(LC_CTYPE, 'de_DE.iso-8859-1');
...
Zend\Search\Lucene\Analysis\Analyzer::setDefault(
new Zend\Search\Lucene\Analysis\Analyzer\Common\Utf8());
...
$doc = new Zend\Search\Lucene\Document();
$doc->addField(Zend\Search\Lucene\Field::UnStored('contents',
strtolower($contents)));
// Title field for search through (indexed, unstored)
$doc->addField(Zend\Search\Lucene\Field::UnStored('title',
strtolower($title)));
// Title field for retrieving (unindexed, stored)
$doc->addField(Zend\Search\Lucene\Field::UnIndexed('_title', $title));
.. code-block:: php
:linenos:
// Searching
setlocale(LC_CTYPE, 'de_DE.iso-8859-1');
...
Zend\Search\Lucene\Analysis\Analyzer::setDefault(
new Zend\Search\Lucene\Analysis\Analyzer\Common\Utf8());
...
$hits = $index->find(strtolower($query));
.. _`mbstring`: http://www.php.net/manual/en/ref.mbstring.php
.. [#] ``Zend\Search\Lucene`` supports only Basic Multilingual Plane (BMP) characters (from 0x0000 to 0xFFFF) and
doesn't support "supplementary characters" (characters whose code points are greater than 0xFFFF)
Java 2 represents these characters as a pair of char (16-bit) values, the first from the high-surrogates
range (0xD800-0xDBFF), the second from the low-surrogates range (0xDC00-0xDFFF). Then they are encoded as
usual UTF-8 characters in six bytes. Standard UTF-8 representation uses four bytes for supplementary
characters.
.. [#] Conversion to 'ASCII//TRANSLIT' may depend on current locale and OS.
For more information about the PHK package format: http://phk.tekwire.net