Fix PHP8.2 str_split function returns empty arrays for empty strings

[HuongNV13]

In PHP 8.2, the str_split function will returns empty arrays for empty strings.
See: https://php.watch/versions/8.2/str_split-empty-string-empty-array

We can use mb_str_split() instead

[CLAassistant]

All committers have signed the CLA.

[fooman]

Unfortunately mb_str_split() was only introduced in php7.4 which will make swapping this out trickier.

[williamdes]

Unfortunately mb_str_split() was only introduced in php7.4 which will make swapping this out trickier.

Thanks for the hint!
Okay, some code needs to be added and use PHP_MAJOR_VERSION const and it's friends

[williamdes]

or maybe just function_exists()

[HuongNV13]

Thanks, everyone.
I have updated the code to use function_exists() to use the correct method.

[MacGritsch]

I think this is not a valid fix as mb_str_split() behaves the same way as str_split() in PHP 8.2 and above.
So why dont check if its an empty string (and if its needed in that case).
Otherwise you could also write a function str_split_old() which returns array('') if the input string is empty.

[survik1]

Looks like incorrect indentation, project uses tabs while this code introduces spaces. Same can be said about all other new lines in this MR.

[nicolaasuni]

Please try to resolve the conflicts.
Could you please instead create a wrapper function in tcpdf_static.php?

[HuongNV13]

Hi Nicola,
Sorry for the late reply, I was busy with my project.
I will update the patch soon.

Thanks,