For example, I have one form for entering a nickname:
<input type='text' name='nick'>
And a field for another text:
<input type='text' name='text'>
How to make it so that when I switched from the nick field to another, the php script was executed and, if necessary, displayed the password field? Without reloading the page naturally.
It is required to check if such a nickname is registered in the system, then when adding text, a person must enter his password.