If you need to parse a string of elements to an array you can use one of the csv functions. You may then merge your arrays.
$array = array('abc');
$string_elements = "'abc1','abc2'";
$array_elements = str_getcsv($string_elements, ',', "'");
$array = array_merge($array, $array_elements);
var_export($array);
Output:
array (
0 => 'abc',
1 => 'abc1',
2 => 'abc2',
)
Alternatively to add each array element to the end of another array you can push them like so using a splat:
array_push($array, ...$array_elements);