debug_zval_dump() now prints "int" instead of "long",
and "float" instead of "double"
dirname() now optionally takes a second parameter,
depth, to get the name of the directory
depth levels up from the current directory.
getrusage() is now supported on Windows.
mktime() and gmmktime() functions
no longer accept
preg_replace() function no longer supports
should be used instead.
setlocale() function no longer accepts
passed as string.
LC_* constants must be used instead.
exec(), system() and passthru()
functions have NULL byte protection now.
shmop_open() now returns a resource instead of an int,
which has to be passed to shmop_size(),
shmop_close() and shmop_delete().
substr() and iconv_substr() now return an empty string,
if string is equal to start characters long.
xml_parser_free() is no longer sufficient to free the
parser resource, if it references an object and this object references that
parser resource. In this case it is necessary to additionally unset the $parser.