How can I split txt file by blank line

Ask how to split the TXT file by blank line,
Ask how to split the TXT file by blank line,
such as TXT file a.txt

The contents are as follows:
Oh, ah, yes.
Uh, uh,

111111
222222

Quack Gaga
Quack Gaga

There is a blank line in it, how to press the blank line to cut it into a paragraph of the string?
------to solve the idea----------------------
If it is a blank line to split it will find two lines (\ r \ n)
$str = ' 123
Defsf

Abc
1213

&* (
';
Print_r (Explode ("\n\r", $str)); Equivalent to Print_r (Explode ("\r\n\r\n", $str));
or use regular
Preg_match ('/[^.] +? (? =\r\n\r\n)/', $STR, $mat);
Print_r ($mat);
------to solve the idea----------------------

$s =<<< TXT
Oh, ah, yes.
Uh, uh,

111111
222222

Quack Gaga
Quack Gaga
TXT;

$a = Preg_split ("/([\r\n]+) \\1/", $s);
Print_r ($a);

Array
(
    [0] Oh ah ah ah
Uh, uh,
    [1] = 111111
222222
    [2] = = Quack Gaga
Quack Gaga
)

