[PHP] Undefined offset:0 Error

When using PHP recently, the page always reported this error:

Undefined offset:0

Because the Error object row is a line of use for a two-dimensional array.
When we examine the logic carefully, we find that the second dimension of the two-bit array does not have the problem of assigning values starting at 0, as follows:

Tdarray[0][0]=1;
tdarray[0][1]=2;
tdarray[1][2]=3;

It should actually be as follows (Tdarray[1][2] should be tdarray[1][0]):

Tdarray[0][0]=1;
tdarray[0][1]=2;
tdarray[1][0]=3;

It's a small problem, but the lack of clarity in logic makes it a little bit more time-consuming to investigate. Let's write it down. Above.
(actually the title forgot to change ...) Welcome to the Markdown Editor ... Ray's dead. ）