I could not find a PHP function to MIME encode the name for a n email address.

Input   = "Karl Müller<kmueller@gmx.de>"
Output = "Karl%20M%FCller<kmueller@gmx.de>"

I wrote it on my own:

<?php
// required to encode names in email addresses    
// replace " " with "%20"
// replace "ü" with "%FC" 
// replace "%" with "%25"      etc....
// Use "%" as Delimiter for MIME
// Use "=" as Delimiter for Quoted Printable
// Input string must be UTF8 encoded
public static function EncodeMime($Text, $Delimiter)
{
    $Text = utf8_decode($Text);
    $Len  = strlen($Text);
    $Out  = "";
    for ($i=0; $i<$Len; $i++)
    {
        $Chr = substr($Text, $i, 1);
        $Asc = ord($Chr);

        if ($Asc > 0x255) // Unicode not allowed
        {
            $Out .= "?";
        }
        else if ($Chr == " " || $Chr == $Delimiter || $Asc > 127) 
        {
            $Out .= $Delimiter . strtoupper(bin2hex($Chr));
        }
        else $Out .= $Chr;
    }
    return $Out;
}
?>