[rfc] str_mask function

Hi everyone, I'm officially starting my work on the ext/intl and standard string functions, and I'm very excited to share my first major proposal for PHP 8.7! I have successfully set up my local development environment and compiler on my machine, and everything is up and running smoothly. As part of this, I would like to propose a new native function called str_mask(). ### Proposal Overview The str_mask() function is designed to securely mask portions of a string using a specified mask character. This is extremely useful for handling sensitive user data like credit card numbers, phone numbers, and tokens. Signature: str_mask(string $string, string $mask_char = '*', int $offset = 0, ?int $length = null): string ### Examples 1. Masking a credit card (positive offset & length): $credit_card = '1234567890123456'; $masked_card = str_mask($credit_card, '*', 4, 8); // Output: 1234********3456 2. Masking a phone number (negative offset to count from the end): $phone_number = '+989123456789'; $masked_phone = str_mask($phone_number, 'X', -4); // Output: +9891234XXXX You can find all the details, implementation plans, and RFC discussions here: https://wiki.php.net/rfc/str_mask Looking forward to hearing your feedback and thoughts! Best regards, Sepehr Mahmoudi