在3d Arrays PHP / Javascript中打印Second级别的数组

I have this array :

A = [S1][P1,P2,P3][S1]
      1      2     3

I want to print the second's array like : 'P1,P2,P3'

I've tried to using for and foreach method. But no use or maybe i have wrong to write the method.

Could you help me about this ?

If you need to print the array key values in JavaScript, you need to use Object.keys.

In your case, running Object.keys(a) will return ["S1","P1,P2,P3"].

If you want to get the array key of the second item in the array, use Object.keys(a)[1].