Update README.md

Author: CodeRevolutionPlugins

README.md

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 # GPT-3-Encoder-PHP
 PHP BPE Text Encoder for GPT-2 / GPT-3
+
+## About
+GPT-2 and GPT-3 use byte pair encoding to turn text into a series of integers to feed into the model. This is a javascript implementation of OpenAI's original python encoder/decoder which can be found [here](https://github.com/openai/gpt-2)
+
+This specific encoder is used in one of my [WordPress plugins](https://coderevolution.ro), to count the number of tokens a string will use when sent to OpenAI API.
+
+
+## Usage
+
+The mbstring PHP extension is needed for this tool to work correctly (in case non-ASCII characters are present in the tokenized text: [details here on how to install mbstring](https://www.php.net/manual/en/mbstring.installation.php)
+
+
+```php
+
+$prompt = "Many words map to one token, but some don't: indivisible. Unicode characters like emojis may be split into many tokens containing the underlying bytes: 🤚🏾 Sequences of characters commonly found next to each other may be grouped together: 1234567890";
+
+$token_array = gpt_encode($prompt);
+
+```
+
+
+