407 lines
14 KiB
PHP
407 lines
14 KiB
PHP
<?php
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/* Copyright (C) 2006-2019 Tobias Leupold <tobias.leupold@gmx.de>
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b8 - A statistical ("Bayesian") spam filter written in PHP
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This program is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation in version 2.1 of the License.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
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*/
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/**
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* The b8 spam filter library
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*
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* @license LGPL 2.1
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* @package b8
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* @author Tobias Leupold <tobias.leupold@gmx.de>
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* @author Oliver Lillie <ollie@buggedcom.co.uk> (original PHP 5 port)
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*/
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namespace b8;
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spl_autoload_register(
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function ($class) {
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$parts = explode('\\', $class);
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if ($parts[1]) {
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require_once __DIR__ . DIRECTORY_SEPARATOR . $parts[1]
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. DIRECTORY_SEPARATOR . $parts[2] . '.php';
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}
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}
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);
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class b8
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{
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const DBVERSION = 3;
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const SPAM = 'spam';
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const HAM = 'ham';
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const LEARN = 'learn';
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const UNLEARN = 'unlearn';
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const CLASSIFIER_TEXT_MISSING = 'CLASSIFIER_TEXT_MISSING';
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const TRAINER_TEXT_MISSING = 'TRAINER_TEXT_MISSING';
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const TRAINER_CATEGORY_MISSING = 'TRAINER_CATEGORY_MISSING';
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const TRAINER_CATEGORY_FAIL = 'TRAINER_CATEGORY_FAIL';
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const INTERNALS_TEXTS = 'b8*texts';
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const INTERNALS_DBVERSION = 'b8*dbversion';
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const KEY_DB_VERSION = 'dbversion';
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const KEY_COUNT_HAM = 'count_ham';
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const KEY_COUNT_SPAM = 'count_spam';
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const KEY_TEXTS_HAM = 'texts_ham';
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const KEY_TEXTS_SPAM = 'texts_spam';
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private $config = [ 'lexer' => 'standard',
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'degenerator' => 'standard',
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'storage' => 'dba',
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'use_relevant' => 15,
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'min_dev' => 0.2,
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'rob_s' => 0.3,
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'rob_x' => 0.5 ];
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private $storage = null;
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private $lexer = null;
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private $degenerator = null;
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private $token_data = null;
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/**
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* Constructs b8
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*
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* @access public
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* @param array b8's configuration: [ 'lexer' => string,
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'degenerator' => string,
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'storage' => string,
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'use_relevant' => int,
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'min_dev' => float,
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'rob_s' => float,
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'rob_x' => float ]
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* @param array The storage backend's config (depending on the backend used)
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* @param array The lexer's config (depending on the lexer used)
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* @param array The degenerator's config (depending on the degenerator used)
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* @return void
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*/
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function __construct(array $config = [],
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array $config_storage = [],
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array $config_lexer = [],
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array $config_degenerator = [])
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{
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// Validate config data
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foreach ($config as $name => $value) {
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switch ($name) {
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case 'min_dev':
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case 'rob_s':
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case 'rob_x':
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$this->config[$name] = (float) $value;
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break;
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case 'use_relevant':
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$this->config[$name] = (int) $value;
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break;
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case 'lexer':
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case 'degenerator':
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case 'storage':
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$this->config[$name] = (string) $value;
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break;
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default:
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throw new \Exception(b8::class . ": Unknown configuration key: \"$name\"");
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}
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}
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// Setup the degenerator class
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$class = '\\b8\\degenerator\\' . $this->config['degenerator'];
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$this->degenerator = new $class($config_degenerator);
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// Setup the lexer class
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$class = '\\b8\\lexer\\' . $this->config['lexer'];
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$this->lexer = new $class($config_lexer);
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// Setup the storage backend
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$class = '\\b8\\storage\\' . $this->config['storage'];
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$this->storage = new $class($config_storage, $this->degenerator);
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}
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/**
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* Classifies a text
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*
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* @access public
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* @param string The text to classify
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* @return mixed float The rating between 0 (ham) and 1 (spam) or an error code
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*/
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public function classify(string $text = null)
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{
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// Let's first see if the user called the function correctly
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if ($text === null) {
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return \b8\b8::CLASSIFIER_TEXT_MISSING;
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}
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// Get the internal database variables, containing the number of ham and spam texts so the
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// spam probability can be calculated in relation to them
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$internals = $this->storage->get_internals();
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// Calculate the spaminess of all tokens
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// Get all tokens we want to rate
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$tokens = $this->lexer->get_tokens($text);
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// Check if the lexer failed (if so, $tokens will be a lexer error code, if not, $tokens
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// will be an array)
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if (! is_array($tokens)) {
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return $tokens;
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}
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// Fetch all available data for the token set from the database
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$this->token_data = $this->storage->get(array_keys($tokens));
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// Calculate the spaminess and importance for each token (or a degenerated form of it)
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$word_count = [];
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$rating = [];
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$importance = [];
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foreach ($tokens as $word => $count) {
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$word_count[$word] = $count;
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// Although we only call this function only here ... let's do the calculation stuff in a
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// function to make this a bit less confusing ;-)
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$rating[$word] = $this->get_probability($word, $internals);
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$importance[$word] = abs(0.5 - $rating[$word]);
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}
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// Order by importance
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arsort($importance);
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reset($importance);
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// Get the most interesting tokens (use all if we have less than the given number)
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$relevant = [];
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for ($i = 0; $i < $this->config['use_relevant']; $i++) {
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if ($token = key($importance)) {
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// Important tokens remain
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// If the token's rating is relevant enough, use it
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if (abs(0.5 - $rating[$token]) > $this->config['min_dev']) {
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// Tokens that appear more than once also count more than once
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for ($x = 0, $l = $word_count[$token]; $x < $l; $x++) {
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array_push($relevant, $rating[$token]);
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}
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}
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} else {
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// We have less words as we want to use, so we already use what we have and can
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// break here
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break;
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}
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next($importance);
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}
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// Calculate the spaminess of the text (thanks to Mr. Robinson ;-)
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// We set both haminess and spaminess to 1 for the first multiplying
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$haminess = 1;
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$spaminess = 1;
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// Consider all relevant ratings
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foreach ($relevant as $value) {
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$haminess *= (1.0 - $value);
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$spaminess *= $value;
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}
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// If no token was good for calculation, we really don't know how to rate this text, so
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// we can return 0.5 without further calculations.
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if ($haminess == 1 && $spaminess == 1) {
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return 0.5;
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}
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// Calculate the combined rating
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// Get the number of relevant ratings
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$n = count($relevant);
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// The actual haminess and spaminess
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$haminess = 1 - pow($haminess, (1 / $n));
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$spaminess = 1 - pow($spaminess, (1 / $n));
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// Calculate the combined indicator
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$probability = ($haminess - $spaminess) / ($haminess + $spaminess);
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// We want a value between 0 and 1, not between -1 and +1, so ...
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$probability = (1 + $probability) / 2;
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// Alea iacta est
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return $probability;
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}
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/**
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* Calculate the spaminess of a single token also considering "degenerated" versions
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*
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* @access private
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* @param string The word to rate
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* @param array The "internals" array
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* @return float The word's rating
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*/
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private function get_probability(string $word, array $internals)
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{
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// Let's see what we have!
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if (isset($this->token_data['tokens'][$word])) {
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// The token is in the database, so we can use it's data as-is and calculate the
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// spaminess of this token directly
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return $this->calculate_probability($this->token_data['tokens'][$word], $internals);
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}
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// The token was not found, so do we at least have similar words?
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if (isset($this->token_data['degenerates'][$word])) {
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// We found similar words, so calculate the spaminess for each one and choose the most
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// important one for the further calculation
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// The default rating is 0.5 simply saying nothing
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$rating = 0.5;
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foreach ($this->token_data['degenerates'][$word] as $degenerate => $count) {
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// Calculate the rating of the current degenerated token
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$rating_tmp = $this->calculate_probability($count, $internals);
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// Is it more important than the rating of another degenerated version?
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if(abs(0.5 - $rating_tmp) > abs(0.5 - $rating)) {
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$rating = $rating_tmp;
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}
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}
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return $rating;
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} else {
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// The token is really unknown, so choose the default rating for completely unknown
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// tokens. This strips down to the robX parameter so we can cheap out the freaky math
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// ;-)
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return $this->config['rob_x'];
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}
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}
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/**
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* Do the actual spaminess calculation of a single token
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*
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* @access private
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* @param array The token's data [ \b8\b8::KEY_COUNT_HAM => int,
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\b8\b8::KEY_COUNT_SPAM => int ]
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* @param array The "internals" array
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* @return float The rating
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*/
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private function calculate_probability(array $data, array $internals)
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{
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// Calculate the basic probability as proposed by Mr. Graham
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// But: consider the number of ham and spam texts saved instead of the number of entries
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// where the token appeared to calculate a relative spaminess because we count tokens
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// appearing multiple times not just once but as often as they appear in the learned texts.
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$rel_ham = $data[\b8\b8::KEY_COUNT_HAM];
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$rel_spam = $data[\b8\b8::KEY_COUNT_SPAM];
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if ($internals[\b8\b8::KEY_TEXTS_HAM] > 0) {
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$rel_ham = $data[\b8\b8::KEY_COUNT_HAM] / $internals[\b8\b8::KEY_TEXTS_HAM];
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}
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if ($internals[\b8\b8::KEY_TEXTS_SPAM] > 0) {
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$rel_spam = $data[\b8\b8::KEY_COUNT_SPAM] / $internals[\b8\b8::KEY_TEXTS_SPAM];
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}
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$rating = $rel_spam / ($rel_ham + $rel_spam);
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// Calculate the better probability proposed by Mr. Robinson
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$all = $data[\b8\b8::KEY_COUNT_HAM] + $data[\b8\b8::KEY_COUNT_SPAM];
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return (($this->config['rob_s'] * $this->config['rob_x']) + ($all * $rating))
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/ ($this->config['rob_s'] + $all);
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}
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/**
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* Check the validity of the category of a request
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*
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* @access private
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* @param string The category
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* @return void
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*/
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private function check_category(string $category)
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{
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return $category === \b8\b8::HAM || $category === \b8\b8::SPAM;
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}
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/**
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* Learn a reference text
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*
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* @access public
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* @param string The text to learn
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* @param string Either b8::SPAM or b8::HAM
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* @return mixed void or an error code
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*/
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public function learn(string $text = null, string $category = null)
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{
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// Let's first see if the user called the function correctly
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if ($text === null) {
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return \b8\b8::TRAINER_TEXT_MISSING;
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}
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if ($category === null) {
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return \b8\b8::TRAINER_CATEGORY_MISSING;
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}
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return $this->process_text($text, $category, \b8\b8::LEARN);
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}
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/**
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* Unlearn a reference text
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*
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* @access public
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* @param string The text to unlearn
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* @param string Either b8::SPAM or b8::HAM
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* @return mixed void or an error code
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*/
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public function unlearn(string $text = null, string $category = null)
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{
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// Let's first see if the user called the function correctly
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if ($text === null) {
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return \b8\b8::TRAINER_TEXT_MISSING;
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}
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if ($category === null) {
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return \b8\b8::TRAINER_CATEGORY_MISSING;
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}
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return $this->process_text($text, $category, \b8\b8::UNLEARN);
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}
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/**
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* Does the actual interaction with the storage backend for learning or unlearning texts
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*
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* @access private
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* @param string The text to process
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* @param string Either b8::SPAM or b8::HAM
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* @param string Either b8::LEARN or b8::UNLEARN
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* @return mixed void or an error code
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*/
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private function process_text(string $text, string $category, string $action)
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{
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// Look if the request is okay
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if (! $this->check_category($category)) {
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return \b8\b8::TRAINER_CATEGORY_FAIL;
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}
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// Get all tokens from $text
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$tokens = $this->lexer->get_tokens($text);
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// Check if the lexer failed (if so, $tokens will be a lexer error code, if not, $tokens
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// will be an array)
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if (! is_array($tokens)) {
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return $tokens;
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}
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// Pass the tokens and what to do with it to the storage backend
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return $this->storage->process_text($tokens, $category, $action);
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}
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}
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