$a  = ('x',);
$b1  = ('x','y1');
$b2  = ('x','y2');
$b3  = ('x','y3');
$b4  = ('x','y4');
$b5  = ('x','y5');
$b6  = ('x','y6');

SELECT $a in ($a, $b1, $b2, $b3, $b4, $b5, $b6)

