md5 is still there (it helps to look at the manual now and then). It is obsolete in its designed role (generating a message digest to detect if a document has been tampered with). It has also never been suitable for hashing passwords for the reason given on its manual page (namely, it's too fast).
otuatail This is not necessarily for passwords but to post data to another page and to store in database tables. Any help on this?
Again, it depends on what you're actually doing (e.g. the above tamper detection), but as NogDog suggests, there is hash
(which can use any of the algorithms listed by https://www.php.net/hash-algos).
The other thing you need to do if you're migrating from one version of PHP to another is to read the Migration sections of the manual, which will list what's been added, removed, and deprecated since each previous version. It will save a lot of guesswork and thrashing around.