$subject = 'abc#
123#
';
$pattern = '/1...$/';
preg_match_all($pattern,$subject,$matches); // no match

$pattern = '/1...(.)$/';

echo bin2hex($matches[1]); // 28

$subject = 'abc#
123#
';
$pattern = '/1...(.)$/';
preg_match_all($pattern,$subject,$matches);
echo bin2hex($matches[1]); // 28
// 28 is equivalent of r or CR(carriage return)

/1...$/m

<?php
// Various OS-es have various end line (a.k.a line break) chars:
// - Windows uses CR+LF (rn);
// - Linux LF (n);
// - OSX CR (r).
// And that's why single dollar meta assertion ($) sometimes fails with multiline modifier (/m) mode - possible bug in PHP 5.3.8(?).
$str="ABC ABCnn123 123rndef defrnop noprn890 890nQRS QRSrr~-_ ~-_";
//          C          3                   p          0                   _
$pat1='/w$/mi';
$pat2='/wr?$/mi';
$pat3='/wR?$/mi';
$pat4='/wv?$/mi';
$n=preg_match_all($pat1, $str, $m1);
$o=preg_match_all($pat2, $str, $m2);
$p=preg_match_all($pat3, $str, $m3);
$r=preg_match_all($pat4, $str, $m4);
echo $str."n1 !!! $pat1 ($n): ".print_r($m1[0], true)
    ."n2 !!! $pat2 ($o): ".print_r($m2[0], true)
    ."n3 !!! $pat3 ($p): ".print_r($m3[0], true)
    ."n4 !!! $pat4 ($r): ".print_r($m4[0], true);
// Note the difference between the three very helpful escape sequences in $pat2 (r), $pat3 (R) and in $pat4 (v) - for some applications at least.

/* The code above results in the following output:
ABC ABC

123 123
def def
nop nop
890 890
QRS QRS

~-_ ~-_
1 !!! /w$/mi (3): Array
(
    [0] => C
    [1] => 0
    [2] => _
)

2 !!! /wr?$/mi (5): Array
(
    [0] => C
    [1] => 3
    [2] => p
    [3] => 0
    [4] => _
)

3 !!! /wR?$/mi (5): Array
(
    [0] => C

    [1] => 3
    [2] => p
    [3] => 0
    [4] => _
)

4 !!! /wv?$/mi (5): Array
(
    [0] => C

    [1] => 3
    [2] => p
    [3] => 0
    [4] => _
)
 */
?>