Description:
------------
when php receivie the data from external sources, a variables named foo[]boo will be saved into $_POST['foo'][];

doc has noted dots and spaces in variable names are converted to underscores. 
@see http://php.net/manual/en/language.variables.external.php

but there no info tell developers variables can't be named `foo[]boo`, otherwise the variable `foo[]boo` should be remove ? 

Test script:
---------------
<form method="post">
    <input type="text" name="id[]" value="1">
    <input type="text" name="id[]_text" value="a">
    <input type="submit">
</form>

Expected result:
----------------
array (
  'id' => 
  array (
    0 => '1',
  ),
)

Actual result:
--------------
array (
  'id' => 
  array (
    0 => '1',
    1 => 'a',
  ),
)