Build encrypter() Function

I need help reconstructing logic from a decrypter() function.
I need an encrypter() function that can encrypt a plaintext string into a format that can be decrypted using the original decrypter() function.
I have attempted to create the encrypter(), but it's not working.

This is my understanding of the decrypter(). Its process is a precise, multi-stage pipeline:

- Obfuscation & Metadata Extraction: It uses two regular expressions to find and extract metadata "hidden" inside the Base64 string. The first sees the three single-digit offsets for the crypto materials, and the second finds the Base64-encoded cipher mode (e.g., Y2Jj for 'cbc').
- Payload Cleaning: It strips this metadata from the Base64 string to get a clean payload.
- Decoding: The cleaned payload is run through base64_decode to get the raw binary data.
- Stateful Cryptographic Extraction: This is the most critical and complex step. The decoder loops backwards (from c=2 down to c=0) to extract the salt, then the IV, then the key. Crucially, after it extracts each 16-byte chunk, it shrinks the payload (substr_replace). This means the offset for the IV is applied to a payload that is 16 bytes smaller, and the offset for the key is applied to a payload that is 32 bytes smaller than the original. The special negative offset for the salt -$offset + $pfx is calculated based on the initial binary payload length.
- Decompression & Decryption: The final, shrunken payload is decompressed with gzinflate and then decrypted with openssl_decrypt.

Using a 16-byte (128-bit) key for a cipher that requires a 32-byte (256-bit) key (aes-256-cbc). It correctly notes that PHP's OpenSSL wrapper silently pads the key with NUL bytes to the required length, a fragile and non-portable behaviour that is the source of instability.

Key tasks include:
- Understanding how the decrypter() function is working
- Reverse engineering to create a working encrypter() function

I am providing two files: one containing the original decrypter() function and my attempt at the encrypter(), and the other file is a detailed analysis of the decrypter() function, which may help you better understand it and make it easier to create the encrypter().