As suggested in the comments, the => can be replaced by : and then json_encode() can be used.
$input = '{"variation"=>[{"accommodationType"=>"test" }]}';
$obj = json_decode(str_replace('=>',':',$input));
var_export($obj);
Result:
(object) array(
'variation' =>
array (
0 =>
(object) array(
'accommodationType' => 'test',
),
),
)
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