diff --git a/.travis.yml b/.travis.yml
index 547e2f1..772c553 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,8 @@
 language: php
 php:
-  - '7.1'
   - '7.2'
   - '7.3'
+  - '7.4'
 
 sudo: false
 
diff --git a/README.md b/README.md
index ccc8b6f..3ad0dea 100644
--- a/README.md
+++ b/README.md
@@ -55,7 +55,7 @@ $classifier->fromJson($stateJson);
 
 Returns an instance of a Naive-Bayes Classifier.
 
-Pass in an optional `options` object to configure the instance. If you specify a `tokenizer` of `iTokenizer` instance in `options`, it will be used as the instance's tokenizer.
+Pass in an optional `options` object to configure the instance. If you specify a `tokenizer` function in `options`, it will be used as the instance's tokenizer.
 
 ### `$classifier->learn(text, category)`
 
diff --git a/composer.json b/composer.json
index 199f647..538bd47 100755
--- a/composer.json
+++ b/composer.json
@@ -26,10 +26,10 @@
   }],
   "type": "library",
   "require": {
-    "php": ">=7.1"
+    "php": ">=7.2"
   },
   "require-dev": {
-    "phpunit/phpunit": "~6.3.0"
+    "phpunit/phpunit": "^8.0"
   },
   "autoload": {
     "psr-4": {
diff --git a/composer.lock b/composer.lock
index ce84441..287a1e5 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,21 +4,21 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "b649912c285ba33ba94e6fcdc8e740eb",
+    "content-hash": "46cbef6e2b8dcc3d78a7c63812d724e6",
     "packages": [],
     "packages-dev": [
         {
             "name": "doctrine/instantiator",
-            "version": "1.2.0",
+            "version": "1.3.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/doctrine/instantiator.git",
-                "reference": "a2c590166b2133a4633738648b6b064edae0814a"
+                "reference": "ae466f726242e637cebdd526a7d991b9433bacf1"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/doctrine/instantiator/zipball/a2c590166b2133a4633738648b6b064edae0814a",
-                "reference": "a2c590166b2133a4633738648b6b064edae0814a",
+                "url": "https://api.github.com/repos/doctrine/instantiator/zipball/ae466f726242e637cebdd526a7d991b9433bacf1",
+                "reference": "ae466f726242e637cebdd526a7d991b9433bacf1",
                 "shasum": ""
             },
             "require": {
@@ -61,20 +61,20 @@
                 "constructor",
                 "instantiate"
             ],
-            "time": "2019-03-17T17:37:11+00:00"
+            "time": "2019-10-21T16:45:58+00:00"
         },
         {
             "name": "myclabs/deep-copy",
-            "version": "1.9.1",
+            "version": "1.9.4",
             "source": {
                 "type": "git",
                 "url": "https://github.com/myclabs/DeepCopy.git",
-                "reference": "e6828efaba2c9b79f4499dae1d66ef8bfa7b2b72"
+                "reference": "579bb7356d91f9456ccd505f24ca8b667966a0a7"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/myclabs/DeepCopy/zipball/e6828efaba2c9b79f4499dae1d66ef8bfa7b2b72",
-                "reference": "e6828efaba2c9b79f4499dae1d66ef8bfa7b2b72",
+                "url": "https://api.github.com/repos/myclabs/DeepCopy/zipball/579bb7356d91f9456ccd505f24ca8b667966a0a7",
+                "reference": "579bb7356d91f9456ccd505f24ca8b667966a0a7",
                 "shasum": ""
             },
             "require": {
@@ -109,26 +109,26 @@
                 "object",
                 "object graph"
             ],
-            "time": "2019-04-07T13:18:21+00:00"
+            "time": "2019-12-15T19:12:40+00:00"
         },
         {
             "name": "phar-io/manifest",
-            "version": "1.0.1",
+            "version": "1.0.3",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phar-io/manifest.git",
-                "reference": "2df402786ab5368a0169091f61a7c1e0eb6852d0"
+                "reference": "7761fcacf03b4d4f16e7ccb606d4879ca431fcf4"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phar-io/manifest/zipball/2df402786ab5368a0169091f61a7c1e0eb6852d0",
-                "reference": "2df402786ab5368a0169091f61a7c1e0eb6852d0",
+                "url": "https://api.github.com/repos/phar-io/manifest/zipball/7761fcacf03b4d4f16e7ccb606d4879ca431fcf4",
+                "reference": "7761fcacf03b4d4f16e7ccb606d4879ca431fcf4",
                 "shasum": ""
             },
             "require": {
                 "ext-dom": "*",
                 "ext-phar": "*",
-                "phar-io/version": "^1.0.1",
+                "phar-io/version": "^2.0",
                 "php": "^5.6 || ^7.0"
             },
             "type": "library",
@@ -164,20 +164,20 @@
                 }
             ],
             "description": "Component for reading phar.io manifest information from a PHP Archive (PHAR)",
-            "time": "2017-03-05T18:14:27+00:00"
+            "time": "2018-07-08T19:23:20+00:00"
         },
         {
             "name": "phar-io/version",
-            "version": "1.0.1",
+            "version": "2.0.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phar-io/version.git",
-                "reference": "a70c0ced4be299a63d32fa96d9281d03e94041df"
+                "reference": "45a2ec53a73c70ce41d55cedef9063630abaf1b6"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phar-io/version/zipball/a70c0ced4be299a63d32fa96d9281d03e94041df",
-                "reference": "a70c0ced4be299a63d32fa96d9281d03e94041df",
+                "url": "https://api.github.com/repos/phar-io/version/zipball/45a2ec53a73c70ce41d55cedef9063630abaf1b6",
+                "reference": "45a2ec53a73c70ce41d55cedef9063630abaf1b6",
                 "shasum": ""
             },
             "require": {
@@ -211,39 +211,37 @@
                 }
             ],
             "description": "Library for handling version information and constraints",
-            "time": "2017-03-05T17:38:23+00:00"
+            "time": "2018-07-08T19:19:57+00:00"
         },
         {
             "name": "phpdocumentor/reflection-common",
-            "version": "1.0.1",
+            "version": "2.0.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phpDocumentor/ReflectionCommon.git",
-                "reference": "21bdeb5f65d7ebf9f43b1b25d404f87deab5bfb6"
+                "reference": "63a995caa1ca9e5590304cd845c15ad6d482a62a"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phpDocumentor/ReflectionCommon/zipball/21bdeb5f65d7ebf9f43b1b25d404f87deab5bfb6",
-                "reference": "21bdeb5f65d7ebf9f43b1b25d404f87deab5bfb6",
+                "url": "https://api.github.com/repos/phpDocumentor/ReflectionCommon/zipball/63a995caa1ca9e5590304cd845c15ad6d482a62a",
+                "reference": "63a995caa1ca9e5590304cd845c15ad6d482a62a",
                 "shasum": ""
             },
             "require": {
-                "php": ">=5.5"
+                "php": ">=7.1"
             },
             "require-dev": {
-                "phpunit/phpunit": "^4.6"
+                "phpunit/phpunit": "~6"
             },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.0.x-dev"
+                    "dev-master": "2.x-dev"
                 }
             },
             "autoload": {
                 "psr-4": {
-                    "phpDocumentor\\Reflection\\": [
-                        "src"
-                    ]
+                    "phpDocumentor\\Reflection\\": "src/"
                 }
             },
             "notification-url": "https://packagist.org/downloads/",
@@ -265,31 +263,32 @@
                 "reflection",
                 "static analysis"
             ],
-            "time": "2017-09-11T18:02:19+00:00"
+            "time": "2018-08-07T13:53:10+00:00"
         },
         {
             "name": "phpdocumentor/reflection-docblock",
-            "version": "4.3.1",
+            "version": "4.3.4",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phpDocumentor/ReflectionDocBlock.git",
-                "reference": "bdd9f737ebc2a01c06ea7ff4308ec6697db9b53c"
+                "reference": "da3fd972d6bafd628114f7e7e036f45944b62e9c"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phpDocumentor/ReflectionDocBlock/zipball/bdd9f737ebc2a01c06ea7ff4308ec6697db9b53c",
-                "reference": "bdd9f737ebc2a01c06ea7ff4308ec6697db9b53c",
+                "url": "https://api.github.com/repos/phpDocumentor/ReflectionDocBlock/zipball/da3fd972d6bafd628114f7e7e036f45944b62e9c",
+                "reference": "da3fd972d6bafd628114f7e7e036f45944b62e9c",
                 "shasum": ""
             },
             "require": {
                 "php": "^7.0",
-                "phpdocumentor/reflection-common": "^1.0.0",
-                "phpdocumentor/type-resolver": "^0.4.0",
+                "phpdocumentor/reflection-common": "^1.0.0 || ^2.0.0",
+                "phpdocumentor/type-resolver": "~0.4 || ^1.0.0",
                 "webmozart/assert": "^1.0"
             },
             "require-dev": {
-                "doctrine/instantiator": "~1.0.5",
+                "doctrine/instantiator": "^1.0.5",
                 "mockery/mockery": "^1.0",
+                "phpdocumentor/type-resolver": "0.4.*",
                 "phpunit/phpunit": "^6.4"
             },
             "type": "library",
@@ -316,41 +315,40 @@
                 }
             ],
             "description": "With this component, a library can provide support for annotations via DocBlocks or otherwise retrieve information that is embedded in a DocBlock.",
-            "time": "2019-04-30T17:48:53+00:00"
+            "time": "2019-12-28T18:55:12+00:00"
         },
         {
             "name": "phpdocumentor/type-resolver",
-            "version": "0.4.0",
+            "version": "1.0.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phpDocumentor/TypeResolver.git",
-                "reference": "9c977708995954784726e25d0cd1dddf4e65b0f7"
+                "reference": "2e32a6d48972b2c1976ed5d8967145b6cec4a4a9"
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             "dist": {
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-                "url": "https://api.github.com/repos/phpDocumentor/TypeResolver/zipball/9c977708995954784726e25d0cd1dddf4e65b0f7",
-                "reference": "9c977708995954784726e25d0cd1dddf4e65b0f7",
+                "url": "https://api.github.com/repos/phpDocumentor/TypeResolver/zipball/2e32a6d48972b2c1976ed5d8967145b6cec4a4a9",
+                "reference": "2e32a6d48972b2c1976ed5d8967145b6cec4a4a9",
                 "shasum": ""
             },
             "require": {
-                "php": "^5.5 || ^7.0",
-                "phpdocumentor/reflection-common": "^1.0"
+                "php": "^7.1",
+                "phpdocumentor/reflection-common": "^2.0"
             },
             "require-dev": {
-                "mockery/mockery": "^0.9.4",
-                "phpunit/phpunit": "^5.2||^4.8.24"
+                "ext-tokenizer": "^7.1",
+                "mockery/mockery": "~1",
+                "phpunit/phpunit": "^7.0"
             },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.0.x-dev"
+                    "dev-master": "1.x-dev"
                 }
             },
             "autoload": {
                 "psr-4": {
-                    "phpDocumentor\\Reflection\\": [
-                        "src/"
-                    ]
+                    "phpDocumentor\\Reflection\\": "src"
                 }
             },
             "notification-url": "https://packagist.org/downloads/",
@@ -363,37 +361,38 @@
                     "email": "me@mikevanriel.com"
                 }
             ],
-            "time": "2017-07-14T14:27:02+00:00"
+            "description": "A PSR-5 based resolver of Class names, Types and Structural Element Names",
+            "time": "2019-08-22T18:11:29+00:00"
         },
         {
             "name": "phpspec/prophecy",
-            "version": "1.8.1",
+            "version": "1.10.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phpspec/prophecy.git",
-                "reference": "1927e75f4ed19131ec9bcc3b002e07fb1173ee76"
+                "reference": "cbe1df668b3fe136bcc909126a0f529a78d4cbbc"
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-                "reference": "1927e75f4ed19131ec9bcc3b002e07fb1173ee76",
+                "url": "https://api.github.com/repos/phpspec/prophecy/zipball/cbe1df668b3fe136bcc909126a0f529a78d4cbbc",
+                "reference": "cbe1df668b3fe136bcc909126a0f529a78d4cbbc",
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             "require": {
                 "doctrine/instantiator": "^1.0.2",
                 "php": "^5.3|^7.0",
-                "phpdocumentor/reflection-docblock": "^2.0|^3.0.2|^4.0",
-                "sebastian/comparator": "^1.1|^2.0|^3.0",
+                "phpdocumentor/reflection-docblock": "^2.0|^3.0.2|^4.0|^5.0",
+                "sebastian/comparator": "^1.2.3|^2.0|^3.0",
                 "sebastian/recursion-context": "^1.0|^2.0|^3.0"
             },
             "require-dev": {
-                "phpspec/phpspec": "^2.5|^3.2",
+                "phpspec/phpspec": "^2.5 || ^3.2",
                 "phpunit/phpunit": "^4.8.35 || ^5.7 || ^6.5 || ^7.1"
             },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.8.x-dev"
+                    "dev-master": "1.10.x-dev"
                 }
             },
             "autoload": {
@@ -426,44 +425,44 @@
                 "spy",
                 "stub"
             ],
-            "time": "2019-06-13T12:50:23+00:00"
+            "time": "2019-12-22T21:05:45+00:00"
         },
         {
             "name": "phpunit/php-code-coverage",
-            "version": "5.3.2",
+            "version": "7.0.10",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/php-code-coverage.git",
-                "reference": "c89677919c5dd6d3b3852f230a663118762218ac"
+                "reference": "f1884187926fbb755a9aaf0b3836ad3165b478bf"
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-                "reference": "c89677919c5dd6d3b3852f230a663118762218ac",
+                "url": "https://api.github.com/repos/sebastianbergmann/php-code-coverage/zipball/f1884187926fbb755a9aaf0b3836ad3165b478bf",
+                "reference": "f1884187926fbb755a9aaf0b3836ad3165b478bf",
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             "require": {
                 "ext-dom": "*",
                 "ext-xmlwriter": "*",
-                "php": "^7.0",
-                "phpunit/php-file-iterator": "^1.4.2",
+                "php": "^7.2",
+                "phpunit/php-file-iterator": "^2.0.2",
                 "phpunit/php-text-template": "^1.2.1",
-                "phpunit/php-token-stream": "^2.0.1",
+                "phpunit/php-token-stream": "^3.1.1",
                 "sebastian/code-unit-reverse-lookup": "^1.0.1",
-                "sebastian/environment": "^3.0",
+                "sebastian/environment": "^4.2.2",
                 "sebastian/version": "^2.0.1",
-                "theseer/tokenizer": "^1.1"
+                "theseer/tokenizer": "^1.1.3"
             },
             "require-dev": {
-                "phpunit/phpunit": "^6.0"
+                "phpunit/phpunit": "^8.2.2"
             },
             "suggest": {
-                "ext-xdebug": "^2.5.5"
+                "ext-xdebug": "^2.7.2"
             },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "5.3.x-dev"
+                    "dev-master": "7.0-dev"
                 }
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             "autoload": {
@@ -489,29 +488,32 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2018-04-06T15:36:58+00:00"
+            "time": "2019-11-20T13:55:58+00:00"
         },
         {
             "name": "phpunit/php-file-iterator",
-            "version": "1.4.5",
+            "version": "2.0.2",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/php-file-iterator.git",
-                "reference": "730b01bc3e867237eaac355e06a36b85dd93a8b4"
+                "reference": "050bedf145a257b1ff02746c31894800e5122946"
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-                "reference": "730b01bc3e867237eaac355e06a36b85dd93a8b4",
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+                "reference": "050bedf145a257b1ff02746c31894800e5122946",
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             },
             "require": {
-                "php": ">=5.3.3"
+                "php": "^7.1"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^7.1"
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             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.4.x-dev"
+                    "dev-master": "2.0.x-dev"
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@@ -526,7 +528,7 @@
             "authors": [
                 {
                     "name": "Sebastian Bergmann",
-                    "email": "sb@sebastian-bergmann.de",
+                    "email": "sebastian@phpunit.de",
                     "role": "lead"
                 }
             ],
@@ -536,7 +538,7 @@
                 "filesystem",
                 "iterator"
             ],
-            "time": "2017-11-27T13:52:08+00:00"
+            "time": "2018-09-13T20:33:42+00:00"
         },
         {
             "name": "phpunit/php-text-template",
@@ -581,28 +583,28 @@
         },
         {
             "name": "phpunit/php-timer",
-            "version": "1.0.9",
+            "version": "2.1.2",
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                 "url": "https://github.com/sebastianbergmann/php-timer.git",
-                "reference": "3dcf38ca72b158baf0bc245e9184d3fdffa9c46f"
+                "reference": "1038454804406b0b5f5f520358e78c1c2f71501e"
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+                "php": "^7.1"
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             "require-dev": {
-                "phpunit/phpunit": "^4.8.35 || ^5.7 || ^6.0"
+                "phpunit/phpunit": "^7.0"
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             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.0-dev"
+                    "dev-master": "2.1-dev"
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@@ -617,7 +619,7 @@
             "authors": [
                 {
                     "name": "Sebastian Bergmann",
-                    "email": "sb@sebastian-bergmann.de",
+                    "email": "sebastian@phpunit.de",
                     "role": "lead"
                 }
             ],
@@ -626,33 +628,33 @@
             "keywords": [
                 "timer"
             ],
-            "time": "2017-02-26T11:10:40+00:00"
+            "time": "2019-06-07T04:22:29+00:00"
         },
         {
             "name": "phpunit/php-token-stream",
-            "version": "2.0.2",
+            "version": "3.1.1",
             "source": {
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-                "reference": "791198a2c6254db10131eecfe8c06670700904db"
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+                "reference": "573381c0a64f155a0d9a23f4b0c797194805b925"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/webmozart/assert/zipball/83e253c8e0be5b0257b881e1827274667c5c17a9",
-                "reference": "83e253c8e0be5b0257b881e1827274667c5c17a9",
+                "url": "https://api.github.com/repos/webmozart/assert/zipball/573381c0a64f155a0d9a23f4b0c797194805b925",
+                "reference": "573381c0a64f155a0d9a23f4b0c797194805b925",
                 "shasum": ""
             },
             "require": {
                 "php": "^5.3.3 || ^7.0",
                 "symfony/polyfill-ctype": "^1.8"
             },
+            "conflict": {
+                "vimeo/psalm": "<3.6.0"
+            },
             "require-dev": {
-                "phpunit/phpunit": "^4.6",
-                "sebastian/version": "^1.0.1"
+                "phpunit/phpunit": "^4.8.36 || ^7.5.13"
             },
             "type": "library",
-            "extra": {
-                "branch-alias": {
-                    "dev-master": "1.3-dev"
-                }
-            },
             "autoload": {
                 "psr-4": {
                     "Webmozart\\Assert\\": "src/"
@@ -1527,7 +1521,7 @@
                 "check",
                 "validate"
             ],
-            "time": "2018-12-25T11:19:39+00:00"
+            "time": "2019-11-24T13:36:37+00:00"
         }
     ],
     "aliases": [],
@@ -1536,7 +1530,7 @@
     "prefer-stable": true,
     "prefer-lowest": false,
     "platform": {
-        "php": ">=7.1"
+        "php": ">=7.2"
     },
     "platform-dev": []
 }
diff --git a/src/Bayes.php b/src/Bayes.php
index 806607a..497c6df 100755
--- a/src/Bayes.php
+++ b/src/Bayes.php
@@ -17,46 +17,66 @@ class Bayes
     ];
 
     /**
+     * hashmap of our category names
+     *
      * @var array
      */
     public $categories;
 
     /**
+     * document frequency table for each of our categories
+     *  for each category, how often were documents mapped to it
+     *
      * @var number
      */
     public $docCount;
 
     /**
+     * number of documents we have learned from
+     *
      * @var number
      */
     public $totalDocuments;
 
     /**
+     * Vocabulary list
+     *
      * @var array
      */
     public $vocabulary;
 
     /**
+     * Vocabulary size
+     *
      * @var number
      */
     public $vocabularySize;
 
     /**
+     * for each category, how many words total were mapped to it
+     *
      * @var number
      */
     public $wordCount;
 
     /**
+     * word frequency table for each category
+     *  for each category, how frequent was a given word mapped to it
+     *
      * @var number
      */
     public $wordFrequencyCount;
 
     /**
+     * constructor options which include tokenizer
+     *
      * @var array
      */
     protected $options;
 
     /**
+     * the tokenizer function
+     *
      * @var function
      */
     protected $tokenizer;
@@ -112,7 +132,6 @@ public function categorize($text)
     public function frequencyTable($tokens)
     {
         $frequencyTable = [];
-        // => for each category, how often were documents mapped to it
         foreach ($tokens as $token) {
             if (!isset($frequencyTable[$token])) {
                 $frequencyTable[$token] = 1;
@@ -279,25 +298,12 @@ public function reset()
             $this->tokenizer = $this->options['tokenizer'];
         }
 
-        // add this word to our vocabulary if not already existing
-        $this->categories = [];
-
-        // update the frequency information for this word in this category
-        // update the count of all words we have seen mapped to this category
-        $this->docCount = [];
-
-        // iterate thru our categories to find the one with max probability
-        $this->totalDocuments = 0;
-
-        // for this text
-        $this->vocabulary     = [];
-        $this->vocabularySize = 0;
-
-        // iterate thru our categories to find the one with max probability
-        $this->wordCount = [];
-
-        // for this text
-        // determine the log of the P( w | c ) for this word
+        $this->categories         = [];
+        $this->docCount           = [];
+        $this->totalDocuments     = 0;
+        $this->vocabulary         = [];
+        $this->vocabularySize     = 0;
+        $this->wordCount          = [];
         $this->wordFrequencyCount = [];
 
         return $this;