Given an ini file that looks like this (quotes added for emphasis):

"[section1]"
foo = bar
blah = ya

"[section2] "
fooz = blat
ya = John YaYa

the resulting array when parsed with parse_ini_file('filename.ini', TRUE) would end up looking much like this:
Array
(
  [section1] = Array
    (
      (
        [foo] => bar
        [blah] => ya
        [fooz] => blat
        [ya] => John YaYa   
      )
    )
)

Eg section1 and  section2 would be merged together under section1 when the line containing marker for section2 did not end with "]"