<?php

$string = implode("\n", range('a', 'c')) . "\n";

$result = array
(
    '~^~' => null,
    '~^~m' => null,
    '~\a~' => null,
    '~\a~m' => null,
    '~\A~' => null,
    '~\A~m' => null,
    '~$~' => null,
    '~$~m' => null,
    '~\z~' => null,
    '~\z~m' => null,
    '~\Z~' => null,
    '~\Z~m' => null,
);

foreach ($result as $key => $value)
{
    $result[$key] = str_replace("\n", '', preg_replace($key, 'X', $string));
}

print_r($result);

?>

Array
(
    [~^~] => Xabc
    [~^~m] => XaXbXcX
    [~\a~] => abc
    [~\a~m] => abc
    [~\A~] => Xabc
    [~\A~m] => Xabc
    [~$~] => abcXX
    [~$~m] => aXbXcXX
    [~\z~] => abcX
    [~\z~m] => abcX
    [~\Z~] => abcXX
    [~\Z~m] => abcXX
)