Training the Spam Filter

Training teaches the classifier which texts are spam and which are ham. The filter learns by counting how often tokens appear in each category, weighted by the total number of trained texts per category.

Basic training

$classifier->learn($text, BinaryClassifier::SPAM);  // mark as spam
$classifier->learn($text, BinaryClassifier::HAM);   // mark as ham

Both constants are defined on BinaryClassifier:

BinaryClassifier::SPAM  // = 'spam'
BinaryClassifier::HAM   // = 'ham'

Unlearning

Remove a previously trained text from the model:

$classifier->unlearn($text, BinaryClassifier::SPAM);
$classifier->unlearn($text, BinaryClassifier::HAM);

Use this to correct mistakes or to remove old training data that no longer reflects current patterns.

Correcting a misclassification

The recommended correction workflow:

// Text was learned as ham but should have been spam
$classifier->unlearn($text, BinaryClassifier::HAM);
$classifier->learn($text, BinaryClassifier::SPAM);

Always unlearn before re-learning with a different label. Skipping the unlearn step adds weight to both categories, which degrades accuracy.

Batch training

There is no bulk training API — call learn() in a loop:

$spamTexts = ['...', '...', '...'];
foreach ($spamTexts as $text) {
    $classifier->learn($text, BinaryClassifier::SPAM);
}

Training data quality

Principle	Guidance
Balance	Aim for a similar number of spam and ham samples
Diversity	Varied text produces better generalisation than repetitive phrases
Relevance	Train on texts representative of what you expect to classify
Maintenance	Periodically untrain outdated samples to keep the model current

Training persistence

Training is persisted immediately to the storage backend. There is no separate "flush" or "commit" step. Rdbms storage writes to the database on every learn() call. DBA storage opens, writes, and closes the file per operation.

Error codes

learn() and unlearn() return null on success or one of:

Constant	Meaning
BinaryClassifier::TRAINER_TEXT_MISSING	$text was null
BinaryClassifier::TRAINER_CATEGORY_MISSING	$category was null
BinaryClassifier::TRAINER_CATEGORY_FAIL	$category was not BinaryClassifier::SPAM or BinaryClassifier::HAM

See Error Codes reference for the full list.