php – Are PHP functions case-sensitive, if not…?

I use a lot of these functions in my PHP code; UID()、user_getProfileImage() ... etc. I write all my projects on Windows and it works fine. No problem here, but when I put my project on my server, it gives an error like this;

fatal error: call /var/www/vhosts/... Undefined function UID().

What the? Is it undefined?!

I’m checking all my project files and again transferring all the files via FTP to the server, again… Same error.

But when I changed the name of UID() to uid() (used in lib.php and elsewhere it is located), it worked great.

So what’s the problem? What’s wrong with this server?

Local PHP version: 5.3.10

Server PHP Information: http://… Deleted

Note: I used Notepad++ to encode all PHP files as “UTF-8 without BOM” (as always), and interestingly another project worked just fine, even using the same features and running on the same server.

Thank you.

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updates (and solutions);

1. Do not use the “I” (uppercase “i”) character in any function name
   or
2. Simply use setlocale like this; setlocale(LC_TIME, "tr_TR. UTF-8") I just need locale time configuration and use it

3. If you need LC_ALL, don’t forget to set the LC_CTYPE in the en_US, i.e.:

   setlocale(LC_ALL, "tr_TR. UTF-8"); setlocale(LC_CTYPE, "en_US");

This implies that there is an “I problem” when PHP uses the Turkish locale (tr_TR, tr_TR.utf8…). When you do this, the check for case-insensitivity between uppercase and lowercase letters “i” fails.

See https://bugs.php.net/18556 — “Set locale to ‘tr_TR’ lowercase class name”

You have several solutions:

• Define and call your function with letters with the same case (or at least the letter “i”); The upper or lower limit does not matter.
• Use a locale that is not affected by this (error) behavior.

The latter is preferred, mainly because it is usually a task that solves all problems with only minor changes.