$array = [
'sorular' => [1,2,3,4,45,44,50],
'cvp1' => 'B',
'cvp2' => 'C',
'cvp3' => 'D',
'cvp44' => 'D',
'cvp45' => 'D'
];

$arr = [];
foreach ($array['sorular'] as $item => $value) :

if (array_key_exists('cvp'.$value, $array)) {
$arr[$value] = $array['cvp'.$value];
} else
$arr[$value] = 'Boş';

endforeach;

echo '
';

print_r($arr);

echo '
';