Php case sensitivity Verification

I have a login registration function. When I successfully registered the user AA, I entered the user with the aa user name and password. I guess it was a problem, I hope I have a login and registration function. When I successfully register a user named AA, I entered the user name with the aa user name and password, I guess it's a problem.

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I have a login registration function. When I successfully registered the user AA, I entered the user with the aa user name and password. I guess it was a problem, hope to give you some advice

Which character set is your database? You can select a bin.

It is best to use uppercase or lowercase letters in a unified manner. The database has no special settings and is case insensitive.

Generally, the user name is converted to lowercase and then stored. the user name should not be case sensitive,
In this case, you should use the user name and password to check the database. If a record is returned, it is considered successful.
A more reasonable approach is to use only the user name for query. After the result is returned, use if for password comparison.

Most databases are case-insensitive by default. If you want to distinguish them, you must first change the default settings of the database.