Tha following is working in index.php, but is it correct?
Before the html tag:
$la= array();
$la['index.php'] = 'Start page';
(Actually this is another language library that is included)
Then inside the header:
<title><?php echo $la[$_SERVER['PHP_SELF']];?></title>
For me the part "$la[$_SERVER['PHP_SELF']]" seams strange, but its working. The title is there in my browser. Is it good practice?
Yes, current code works. If it's good practice is up for debate.
PHP (like many other language) will evaluate the statements in order. Everytime you use the brackets you are really using the arrays index operator where the index acts as the parameter.
Your code will first evaluate the $_SERVER['PHP_SELF'] statement which probably returns 'index.php'. The next call will be $la['index.php'] (since that was what your inner statement returned. This will in turn return the value 'Start page' which is what is sent to the echo.
There's nothing wrong with your code. The superglobal $_SERVER['PHP_SELF'] holds the name of the current file. It's not very secure because it can be manipulated to execute arbitrary code if you inject it without sanitizing it properly.
$_SERVER['PHP_SELF']can be tampered with, so it is not ok (as in good practice). of course we do not know what measures have been taken to make it safe. or not.