how to decode the subject in an email?

Question

I have send a mail with Subject line as

[BILLING #PHY-945-49853]: [Ticket #12622] Payment Method

But in the source of the message the line is like below

Subject: =?UTF-8?B?W1NBTEVTICNCQk4tOTM1LTM3OTE3XTogW1RpY2tldCAjMTI2MjJdIFBheW1lbnQ=?=
=?UTF-8?B?IE1ldGhvZA==?=

It is encoded in Base64. How can I decode it back to the original subject line in English using php? I have tried with the php base64_decode($subject) but it does not decode it to the original subject ([BILLING #PHY-945-49853]: [Ticket #12622] Payment Method)

I'm also attaching a sample email message:

Return-Path: .........
X-Original-To: ..........
Delivered-To: ........
Received: ......
X-DKIM: ........
Received:....
To: ....
Subject: =?UTF-8?B?W1NBTEVTICNCQk4tOTM1LTM3OTE3XTogW1RpY2tldCAjMTI2MjJdIFBheW1lbnQ=?=
=?UTF-8?B?IE1ldGhvZA==?=
From: =?UTF-8?B?U0FWVllFSE9TVElORyBTQUxFUw==?=
X-Priority: ..
X-MSMail-Priority: normal
X-MimeOLE: Produced By Kayako Fusion v4.01.204
X-Mailer: Kayako Fusion v4.01.204
Reply-To: .......
Date: .....
Content-Type: multipart/alternative;
boundary="=_1.64496c432f57488924404b338155a2d7"
MIME-Version: 1.0
Message-Id: ....

This is a message in MIME Format. If you see this, your mail reader does not support this format.

--=_1.64496c432f57488924404b338155a2d7
Content-Type: text/plain;
charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline


------------------------------------------------------
Support Center:
Content-Type: text/html;
charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

Answer 1

You're probably looking for iconv_mime_decode.

From the link:

string iconv_mime_decode ( string $encoded_header [, int $mode = 0 [, string $charset = 
ini_get("iconv.internal_encoding") ]] )

Decodes a MIME header field.

Your example:

echo iconv_mime_decode($string);

Yields:

Subject: [SALES #BBN-935-37917]: [Ticket #12622] Payment