How bad is mb_internal_encoding("UTF-8"); ??

Question

Hi ,

After Answering this question

http://stackoverflow.com/questions/4041968/zend-cache-after-loading-cached-data-character-encoding-seems-messed-up/4043064#4043064

I use it to change the PHP's internal encoding , its originally ISO-8859-1 ,

so i need to change the encoding of every none English input value , bu using it i force php to convert every value to UTF-8 Equivalent , as you might see in the question linked above , I am Caching arabic text in files using Zend_cache i wasn't be able to do it with out of that function

I need to know how bad is to use this function mb_internal_encoding("UTF-8"); I had adopt to use this function in every project i opt in , ALL of them are using none english characters

How bad really it is mb_internal_encoding("UTF-8"); ?

if you had any better solution please share it with SO

Thanks