问题
This code
print mb_substr('éxxx', 0, 1);
prints an empty space :(
It is supposed to print the first character, é. This seems to work however:
print mb_substr('éxxx', 0, 2);
But it's not right, because (0, 2) means 2 characters...
回答1:
Try passing the encoding parameter to mb_substr, as such:
print mb_substr('éxxx', 0, 1, 'utf-8');
The encoding is never detected automatically.
回答2:
In practice I've found that, in some systems, multi-byte functions default to ISO-8859-1 for internal encoding. That effectively ruins their ability to handle multi-byte text.
Setting a good default will probably fix this and some other issues:
mb_internal_encoding('UTF-8');
来源：https://stackoverflow.com/questions/13953248/php-mb-substr-not-working-correctly