In PHP, function names are case-insensitive. This means that you can call a function using a different case than the one it was defined with, and PHP will still recognize it as the same function. For example, if you define a function called “myFunction”, you can call it using “myfunction”, “myFunction”, or “MYFUNCTION”, and it will still work as expected.

However, this only applies to the function name itself. The rest of the code in the function, including variables and other language constructs, is still case-sensitive, just like in any other PHP code. This means that you need to be careful to use the correct case when writing your function code, or you may encounter errors or unexpected behavior.

In addition to function names, PHP is also case-insensitive when it comes to certain other language constructs, such as class names and constants. However, there are some exceptions to this rule, such as variable names, which are case-sensitive in PHP.

Overall, it is generally a good idea to be consistent with the case you use when writing your PHP code, including when defining functions. This can help to make your code easier to read and understand, and can help to prevent mistakes and errors that can be caused by using the wrong case. So, it is always a good practice to use the same case consistently throughout your code.