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File: sqlite_fulltextsearch.class.php

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  Classes of Setec Astronomy  >  SQLite Full Text Search  >  sqlite_fulltextsearch.class.php  >  Download  
File: sqlite_fulltextsearch.class.php
Role: Class source
Content type: text/plain
Description: sqlite_fulltextsearch Class file
Class: SQLite Full Text Search
Add Full Text Search SQL commands to SQLite
Author: By
Last change: Added the wordpreparation method.
Date: 9 years ago
Size: 5,065 bytes
 

Contents

Class file image Download
<?php

class sqlite_fulltextsearch {

    var
$_againsts_cache = array ();
   
    var
$use_against_cache = false;
    var
$word_separators_pattern = "/[\s\.,'\"\/\|]+/";
   
    function
sqlite_fulltextsearch () {
       
$this->_againsts_cache = array ();
       
$this->use_against_cache = false;
    }

    function
wordspreparation (&$string, &$against) {
       
// do nothing here, override in subclasses, see sqlite_fulltextsearchex example
   
}
   
    function
_wordspreparation ($string, $against, $usecase, &$string_words, &$against_words, &$string_words_count, &$against_words_count) {
        if (!
$usecase) {
           
$string = strtolower ($string);
           
$against = strtolower ($against);
        }
       
       
$this->wordspreparation ($string, $against);
       
       
$string_words = preg_split ("/ +/", preg_replace ($this->word_separators_pattern, ' ', $string));
       
$against_words = null;

        if (
$this->use_against_cache && isset ($this->_againsts_cache[$against])) {
           
$against_words = $this->_againsts_cache[$against];
        } else {
           
$against_words = preg_split ("/ +/", preg_replace ($this->word_separators_pattern, ' ', $against));
            if (
$this->use_against_cache) {
               
$this->_againsts_cache[$against] = $against_words;
            }
        }
       
       
$string_words_count = count ($string_words);
       
$against_words_count = count ($against_words);
       
        return
true;
    }

    function
prominence ($position, $string_words_count, $against_words_count) {
       
/* lenear prominence */
       
return $position;
    }

    function
_internal_wordprominence ($string_words, $against_words, $string_words_count, $against_words_count) {

        if (
$string_words_count == 0) {
            return
0;
        }
               
       
$global_prominance = 0;
        foreach (
$against_words as $against_word) {
            foreach (
$string_words as $position => $string_word) {
               
$position++;
                if (
$string_word == $against_word) {
                   
$global_prominance += $this->prominence ($position, $string_words_count, $against_words_count);
                }
            }
        }
       
       
$divisor = ($string_words_count + 1) * ($string_words_count / 2); // sum of N integer numbers from 1 to N
       
       
$result = $global_prominance / $divisor;
       
        return
$result;
    }

    function
_wordprominence ($string, $against, $usecase) {
       
       
$this->_wordspreparation ($string, $against, $usecase, &$string_words, &$against_words, &$string_words_count, &$against_words_count);
       
       
$string_words = array_reverse ($string_words);

       
$result = $this->_internal_wordprominence ($string_words, $against_words, $string_words_count, $against_words_count);
       
        return
$result;
    }

    function
_reversewordprominence ($string, $against, $usecase) {

       
$this->_wordspreparation ($string, $against, $usecase, &$string_words, &$against_words, &$string_words_count, &$against_words_count);
       
       
$result = $this->_internal_wordprominence ($string_words, $against_words, $string_words_count, $against_words_count);
       
        return
$result;
    }
   
    function
_centerwordprominence ($string, $against, $usecase) {
       
       
$this->_wordspreparation ($string, $against, $usecase, &$string_words, &$against_words, &$string_words_count, &$against_words_count);
       
       
/* begin centering keywords, from 'a, b, c, d, e' to 'c, d, b, e, a' */
       
$start = ceil ($string_words_count / 2) - 1;
       
$left = $start;
       
$right = $start;
       
$centered_string_words = array ();
       
$centered_string_words[] = $string_words[$start];
        while ((
$left > 0) && ($right < $string_words_count)) {
           
$left--;
           
$right++;
           
$centered_string_words[] = $string_words[$right];
           
$centered_string_words[] = $string_words[$left];
        }
       
        if (
$right < $string_words_count - 1) {
           
$centered_string_words[] = $string_words[$string_words_count - 1];
        }
       
/* end centering keywords */

       
$centered_string_words = array_reverse ($centered_string_words);

       
$result = $this->_internal_wordprominence ($centered_string_words, $against_words, $string_words_count, $against_words_count);
       
        return
$result;
    }
   
    function
_fulltextsearch ($string, $against, $usecase) {
       
       
$result = 0;
   
       
$this->_wordspreparation ($string, $against, $usecase, &$string_words, &$against_words, &$string_words_count, &$against_words_count);
       
        if (
$string_words_count == 0) {
            return
$result;
        }
               
       
$string = ' ' . implode (' ', $string_words) . ' ';
       
$against_ex = ' ';
        for (
$from = 0; $from < $against_words_count; $from++) {
           
$against_ex .= $against_words[$from] . ' ';
           
$result += (substr_count ($string, $against_ex) * ($from + 1)) / $string_words_count;
        }
   
        return
$result;
    }
   
    function
register (&$dbhandle) {
       
sqlite_create_function ($dbhandle, 'fulltextsearch', array (&$this, '_fulltextsearch'), 3);
       
sqlite_create_function ($dbhandle, 'wordprominence', array (&$this, '_wordprominence'), 3);
       
sqlite_create_function ($dbhandle, 'reversewordprominence', array (&$this, '_reversewordprominence'), 3);
       
sqlite_create_function ($dbhandle, 'centerwordprominence', array (&$this, '_centerwordprominence'), 3);
    }

}

?>