Using Chinese fonts in TCPDF and FPDI. Encoding problems - utf-8

Question

I am writing a script that generates Chinese character worksheets (so students can generate and practice writing)
The script is passed a 15 character string from a form in index.php.
The string is then exploded into an array of 15 elements (each a Chinese character).
The problem arises when I want to use the Write() function to populate the file with these characters, I've used the input to pick appropiate images without any problems but now it's the encoding of the fonts that gives me a hard time.
PS. I need to use a cursive/handwritten font as default 'print' fonts are not suitable for handwriting practice.
Ideally I would like to use HDZB_36.TTF or Sharp Regular Script Font
See the code below as well as images of errors I get with some different fonts.
<?php
header('Content-Type: text/html; charset=utf-8');
// linking TCPDF and FPDI libraries
require_once('tcpdf/tcpdf.php');
require_once('fpdi/fpdi.php');
// First retrieve a 15 chinese charcters long string from POST form in index.php
$hanzi = $_POST["hanzi"];
// Explode the hanzi into a 15 items array
function mb_str_split($hanzi){
return preg_split('/(?<!^)(?!$)/u', $hanzi);
}
$charlist = mb_str_split($hanzi);
// Define starting y positions of each line of the grid
$yPos1 = 10.71;
$yPos2 = 17.94;
// Creating new page with PDF as a background
$pdf = new FPDI();
$background = $pdf->setSourceFile('images/worksheet_template1.pdf');
$tplIdx = $pdf->importPage(1);
$pdf->AddPage();
$pdf->useTemplate($tplIdx, 0, 0, 210, 285, false);
/*
This is where the problem starts, I can manage to display latin characters using helvetica
but when I use any of the chinese fonts (usually encoded as GB2312 or BIG5) it fails.
With some larger (ex. stsong) fonts I get a browser error saying: No data received ERR_EMPTY_RESPONSE (Image 1)
With font 'htst3' the characters appeared upside down and were full of artifacts (Image 2).
With font HDZB_36 the characters were not rendered at all.
Other fonts will result in all of the chars displayed as '?' (Image 3)
*/
$fontname = TCPDF_FONTS::addTTFfont('ukai.ttf', 'TrueTypeUnicode', '', 64);
$pdf->SetFont('ukai','', 20);
for ($i = 0; $i <= 14; $i++){
// Generating path of the stroke order image (that works fine)
$sImgPath = "images/x-s.png";
$sImgPath = str_ireplace('x', $charlist[$i], $sImgPath);
// Stroke order image
$pdf->Image($sImgPath, '14', $yPos1, '','5');
// Here we will populate grid of the worksheet with chinese characters as TEXT
$pdf->SetXY(12.4,$yPos2);
$pdf->SetTextColor(0, 0, 0);
$pdf->Write(0, $charlist[$i], '', false);
$pdf->SetXY(24.2,$yPos2);
$pdf->SetTextColor(192,192,192);
$pdf->Write(0, $charlist[$i], '', false);
// Increase the y pos values so the next run of for() will draw in another line
$yPos1 = $yPos1+17.83;
$yPos2 = $yPos2+17.78;
}
ob_clean();
$pdf->Output('worksheet.pdf', 'I');
?>

Answer 1

Just a suggestion:
The file you generate worksheet.pdfshould perhaps have the same encoding as your letters.
The PDF should have the appropriate encoding, see: https://stackoverflow.com/a/10656899/1933185