Undefined Array Key Error in Font Insertion

[Diar44]

Hello,

I encountered an issue when trying to insert a font into my PDF using TCPDF. The following code results in an error:

$pdf->font->insert($pdf->pon, 'helvetica', '', 10, 2, 2, $this->getParameter('k_path_fonts') . "/helvetica.json");
The error message is as follows:

Uncaught PHP Exception ErrorException: "Warning: Undefined array key 1" at Stack.php line 583
Upon reviewing the Stack.php file, I found that the issue is related to the code in lines 579–588, which deals with assigning the font bounding box values:

$this->metric[$mkey]['fbbox'] = [
// left
((float) $tbox[0] * $wratio),
// bottom
((float) $tbox[1] * $cratio),
// right
((float) $tbox[2] * $wratio),
// top
((float) $tbox[3] * $cratio),
];
The problem is that in my case, the $tbox array only contains tbox[0], and tbox[1] is missing, causing the undefined key error.

As a workaround, I modified the code to use the null coalescing operator (??) to provide default values in case any of the indices are missing:

$this->metric[$mkey]['fbbox'] = [
((float) ($tbox[0] ?? 0) * $wratio),
((float) ($tbox[1] ?? 0) * $cratio),
((float) ($tbox[2] ?? 0) * $wratio),
((float) ($tbox[3] ?? 0) * $cratio),
];
This approach resolved the issue for me. However, I am unsure if this is the best solution or if a more appropriate fix should be applied.

Could you please advise on whether this is a suitable fix, or if there might be a deeper issue with the $tbox array that needs to be addressed?

Best regards,
Diar