Replace with Dynamic variable in preg_replace

Hi
I'm trying the following code:

$t = '12<-- AB_C -->';
$AB_C = 'abc';
echo preg_replace('/\<-- ([A-Z_]+) --\>/', "$$1", $t);

Code (markup):

I want to get "12abc" , but it outputs: 12$AB_C , so, it not recognize the replacement as dynamic variable.
Is it any way to use the matched word in preg_replace() as a variable, or dynamic variable?

 

For those who look for a solution to this problem, the '/e' flag, which evalates the replacement, solved the problem, and returns the results i want, using:

preg_replace('/\<-- ([A-Z_]+) --\>/e', "$$1", $t);

Code (markup):

 

Thanks, i code regular in PHP and didn't no that! Thanks for letting us no after you found a solution!

 

this is a similar

echo str_replace('<-- AB_C -->', $AB_C, $t);

Code (markup):