can you elaborate on "threadsafe" restrictions?

[boussou]

In the doc you say there are limitation, but You don't say much about what this mea::

• Global variable is unsafe in per request
  • shall we avoid using them?
  • shall it be considered as un-initialized? and reinit them each request?
• Static variable of a class is unsafe in per request
  • shall we avoid using them?
  • shall it be considered as un-initialized? and reinit them each request?
• Do not design singleton mode
  • very unclear why it is unsafe.
  • can you elaborate and give a faulty example?
• The native IO function works fine, but it slows down nginx
  • can you wirte the function name explicitly?

We use PHP 5.6, it is safe to use ngx_php5 ?

Thanks