creating variable name by concatenating strings in php

Just use $question12[0]. It will give you the desired output.

Using the $var you can do it like this:-

$question = ${'question'. $var}[index];

You're looking for variable variables.

$id = 12;
$q = "question{$id}";
$q = $$q[0];

You should seriously consider looking into multidimensional arrays to stop having multiple arrays.

Variable variable is not recommended, but the answer is below:

$question = ${'question'.$var}[0];