utf8 to ISO-8859-1 not converting some characters correctly through Curl

Question

I have an application that is taking UTF8 encoded characters and needs to send them as part of xml through curl with ISO-8859-1 encoding.

This is my test code:

header('Content-Type: text/plain; charset=IS0-8859-1');

$message = '§ ° " @ # € % & / ( ) = + ` ´ ^ ¨ * - _ : . ; ,';

echo mb_convert_encoding($message, 'ISO-8859-1', 'UTF-8');

//build xml to post
$content =
    '<?xml version="1.0" encoding="ISO-8859-1"?>
    <mobilectrl_sms>
        <header>
            <customer_id>'.CUSTOMER_ID.'</customer_id>
            <password>'.PASSWORD_ID.'</password>
        </header>
        <payload>
            <sms account="'.SHORT_CODE.'">
                <message><![CDATA['.mb_convert_encoding($message, 'ISO-8859-1', 'UTF-8').']]></message>
                <to_msisdn>[phone]</to_msisdn>
            </sms>
        </payload>
    </mobilectrl_sms>';

$posturl = MT_URL;
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $posturl);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, Array("Content-Type: text/xml", "Content-length: ".strlen($content), "charset=ISO-8859-1"));
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_POSTFIELDS, $content);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
$response = curl_exec($ch);

In the browser it almost works, I see § ° " @ # ? % & / ( ) = + ` ´ ^ ¨ * - _ : . ; ,

notice the Euro Sign €

But when it comes through as a text message I am seeing § ? " @ # ? % & / ( ) = + ? ? ^ ? * - _ : . ; ,

I can't figure it out, I've tried utf8_decode also but that seems to make it worse. Am I missing something?

Thanks

Solution 1

There is no euro sign in ISO-8859-1, so it gets substituted with a question mark. There's nothing you can do about it, except choosing something else to substitute it with.

The same goes for the other characters that get converted to ?s.

Solution 2

Some SMS protocols accepts "%80" for the Euro sign. So you could try substituting the "€" with "%80" and URL-encode the rest of the string using ISO-8859-1. It worked for me for some SMS protocols.