How to make a variable composed of multiple PHP variables-php Tutorial

How can multiple PHP variables form a variable? $ Xx [d1] [2] Hello !; $ Axx; $ b1; I have tried the following statements, no. Echo & nbsp; $ {$ a. [d. $ B.] [1]}; how to make a variable as an output? ------ Solution ---------------------- $ xx [d1] [2] Hello !; $ Axx; $ b1; how do multiple variables in ec PHP form one variable?
$ Xx ['d1 '] [2] = 'Hello! ';

$ A = 'XX ';
$ B = '1 ';


I have tried the following statements, no.
Echo $ {$ a. '["d'. $ B.'"] [1] '};


How to make up a variable for output?
------ Solution ----------------------

$ Xx ['d1 '] [2] = 'Hello! ';

$ A = 'XX ';
$ B = '1 ';

Echo $ {$ a} ['d'. $ B] [2];

Is that true?
------ Solution ----------------------

$ Array = array (1 => 'A', 2 => 'B ');
$ Name = 'array ';
$ Key = 1;
Echo $ {$ name} [$ key];

------ Solution ----------------------
Echo $ {$ a} ['d'. $ B] [1];
------ Solution ----------------------

$ Xx ['d1 '] [2] = 'abc ';

$ A = 'XX ';
$ B = '1 ';

Echo $ {$ a} ['d'. $ B] [2];