Filesystem case-sensitivity is not a PHP setting, but rather specific to the OS and filesystem. Windows filesystems tend to be case-insensitive, while most other operating systems prefer case-sensitive filesystems.
Since you cannot necessarily predict what OS your code will run on in the future, it is recommended to always code for case-sensitive fileystems.
If you are currently developing on Windows (or any other OS with case-insensitive filesystems), the best course of action is to return to your code and fix all the file paths to use the correct casing, matching what they are named on disk.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…