I'm getting this error on multiple occasion in a script (invoiceplane) I have been using for a few years now but which hasn't been maintained unfortunately by its creators:
Message: Trying to access array offset on value of type null
My server has been upgrade to PHP 7.4 and I'm looking for a way to fix the issues and maintain the script myself since I'm very happy with it.
This is what's on the line that gives the error:
$len = $cOTLdata['char_data'] === null ? 0 : count($cOTLdata['char_data']);
$cOTLdata is passed to the function:
public function trimOTLdata(&$cOTLdata, $Left = true, $Right = true)
{
$len = $cOTLdata['char_data'] === null ? 0 : count($cOTLdata['char_data']);
$nLeft = 0;
$nRight = 0;
//etc
It's included in mpdf btw, but simply overwriting the files from the github repository did not fix the errors.
This happens because $cOTLdata is not null but the index 'char_data' does not exist. Previous versions of PHP may have been less strict on such mistakes and silently swallowed the error / notice while 7.4 does not do this anymore.
To check whether the index exists or not you can use isset():
isset($cOTLdata['char_data'])
Which means the line should look something like this:
$len = isset($cOTLdata['char_data']) ? count($cOTLdata['char_data']) : 0;
Note I switched the then and else cases of the ternary operator since === null is essentially what isset already does (but in the positive case).
Source: Stackoverflow.com