private function quotedPrintableEncode($input, $line_max = 250)
    {
        $hex = array('0','1','2','3','4','5','6','7',
            '8','9','A','B','C','D','E','F');
        $lines = preg_split("/(?:\r\n|\r|\n)/", $input);
        $linebreak = "=0D=0A=\r\n";
        /* the linebreak also counts as characters in the mime_qp_long_line
         * rule of spam-assassin */
        $line_max = $line_max - strlen($linebreak);
        $escape = "=";
        $output = "";
        $cur_conv_line = "";
        $length = 0;
        $whitespace_pos = 0;
        $addtl_chars = 0;
        
        // iterate lines
        for ($j = 0; $j < count($lines); $j++) {
            $line = $lines[$j];
            $linlen = strlen($line);
            
            // iterate chars
            for ($i = 0; $i < $linlen; $i++) {
                $c = substr($line, $i, 1);
                $dec = ord($c);
                
                $length++;
                
                if ($dec == 32) {
                    // space occurring at end of line, need to encode
                    if (($i == ($linlen - 1))) {
                        $c = "=20";
                        $length += 2;
                    }
                    
                    $addtl_chars = 0;
                    $whitespace_pos = $i;
                } else if (($dec == 61) || ($dec < 32 ) || ($dec > 126)) {
                    $h2 = floor($dec/16);
                    $h1 = floor($dec%16);
                    $c = $escape . $hex["$h2"] . $hex["$h1"];
                    $length += 2;
                    $addtl_chars += 2;
                }
                
                // length for wordwrap exceeded, get a newline into the text
                if ($length >= $line_max) {
                    $cur_conv_line .= $c;
                    
                    // read only up to the whitespace for the current line
                    $whitesp_diff = $i - $whitespace_pos + $addtl_chars;
                    
                    //the text after the whitespace will have to be read
                    // again ( + any additional characters that came into
                    // existence as a result of the encoding process after the whitespace)
                    //
                    // Also, do not start at 0, if there was *no* whitespace in
                    // the whole line
                    if (($i + $addtl_chars) > $whitesp_diff) {
                        $output .= substr($cur_conv_line, 0, (strlen($cur_conv_line) -
                            $whitesp_diff)) . $linebreak;
                            $i =  $i - $whitesp_diff + $addtl_chars;
                    } else {
                        $output .= $cur_conv_line . $linebreak;
                    }
                    
                    $cur_conv_line = "";
                    $length = 0;
                    $whitespace_pos = 0;
                } else {
                    // length for wordwrap not reached, continue reading
                    $cur_conv_line .= $c;
                }
            } // end of for
            
            $length = 0;
            $whitespace_pos = 0;
            $output .= $cur_conv_line;
            $cur_conv_line = "";
            
            if ($j<=count($lines)-1) {
                $output .= $linebreak;
            }
        } // end for
        
        return trim($output);
    }