This is an implementation of mkpasswd -m sha-512 in PHP.
For those poor souls that don't have mkpasswd.c or have crypt() library broken on their systems and cannot use Python implementation (I am looking at you OSX/macOS), or generally dislike Python or Ruby and would rather use PHP.
PHP 5.6 or 7.0+ installed on your system.
If not already downloaded, download the script and make it executable.
chmod +x ./mkpasswd.php
Run it
./mkpasswd.php
The script will ask you for your password first, then for the confirmation of the password, and will generate SHA-512 hash with salt, that is ready for copy/pasting into your /etc/shadow.
e.g:
$6$yAABw15fB8n$Fc4451LE5/JP3R1Y3lQwGz4yva/x.C/v19MMrYfpsVE1s8aAGLqmDpCMKqAg/gT2PaK428smreEszKYUXcgkn1
Maybe add other hashing options.
WARNING: The script is designed to work in non-destructive way. But you are using it at your own peril. I cannot be liable for Earth standing still, your cat getting possessed or your computer bursting in flames.
copyleft. (CC BY-SA 4.0) Do whatever you want with it.