Undefined index: num_cols in milon\\barcode\\src\\Milon\\Barcode\\DNS2D.php:189

[Tarhex]

Got this error when I increased the size of the text to be converted to QrCode.

What is the maximum text size required?

[nightwalkeryao]

I am having this exact same issue. Actually the limit is 1148 characters (UTF-8 encoded).
I firstly thought that it was a problem with the package then I tried some other packages (tecnickcom/tcpdf, jucksearm/php-barcode). I found out that all these packages are actually using an exact same class implementation to generate 1D/2D barcodes. So different package name but same error.