$re = '/(\\\\")([^\\\\n]*)(\\\\n)([^\\\\n]*)(\\\\")/';
$str = 'companyaddress2\\r\\nmultiple1,\\"my address row 1\\nmy address row 2\\",12345,\\"my address 22222 row 1\\nmy address 2222 row 2\\"\\r\\n';
$subst = "$2 $4";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php