Arrays values not identical (but they are?)

Question

I have two arrays. They seem to contain at least one identical set of values, but performing array_diff() does not return anything even though I think it should!

Answer 1

There is probably a character that is non-printable.

Write out both strings into a file, from PHP, in binary format, and compare the results with a hex editor or similar. Just copying the strings and then comparing will not do for some cases as it might lose characters.