How to generate unique strings in php?

How to use php to generate unique strings?
Similar to the string that will appear at the end of youtube: 6Af6b_wyiwI (acceptable characters in the URL)
And is it case-sensitive?
And you can set the length of the string that appears each time
For example, 4~7 random
will become ga79e aa09gsw awe9f and so on (it will change like this every time

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How to use php to generate unique strings?
Just like the string that will appear at the end of youtube: 6Af6b_wyiwI (acceptable characters in the URL)
And is it case-sensitive?
And you can set the length of the string that appears each time
For example, 4~7 random
will become ga79e aa09gsw awe9f and so on (it will change like this every time

It is recommended to use timestamp, which can be encrypted by MD5 or SHA1, but the length is fixed and case-fixed. It can be intercepted, or you can define the encryption rules yourself. If you define it yourself, you can set the desired length. There is no possibility of duplication in this way (an impossible event)
If you define the string yourself and then obtain it randomly, there is a possibility of duplication (a small probability event).
If you just write the URL
You can also refer to segmentfault’s URL writing method

https://segmentfault.com/q/10...

Generate a sequentially growing sequence, and then convert it to a string through ascii code

PHP decimal and hexadecimal conversion:

<code>echo gmp_strval(gmp_init('9876543210', 10), 62)."\n"; //AmOy42
echo gmp_strval(gmp_init('AmOy42', 62), 10)."\n";     //9876543210</code>

The AmOy42 above should be the "string" you want. In fact, it is a 62-base number.
62-base (10+26+26) uses 10 numbers + 26 lowercase letters + 26 uppercase letters. Represents a numerical value, thereby greatly reducing the number of digits.
9876543210 is the self-increasing ID in the database, thus achieving uniqueness.

Let’s talk about a simple method, use hash algorithms such as sha256 to obtain binary data (instead of hexadecimal strings), and then use base64 to encode it

This reference short link generation method is OK