还是php的概率的有关问题，求解说

<br />
Array<br />
(<br />
????[1] => 1<br />
????[2] => 5<br />
????[3] => 10<br />
????[4] => 12<br />
????[5] => 22<br />
????[6] => 50<br />
)

function get_rand($proArr) { <br />
????$result = ''; <br />
????//概率数组的总概率精度 <br />
????$proSum = array_sum($proArr); <br />
????//概率数组循环 <br />
????foreach ($proArr as $key => $proCur) { <br />
????????$randNum = mt_rand(1, $proSum); <br />
????????if ($randNum <= $proCur) { <br />
????????????$result = $key; <br />
????????????break; <br />
????????} else { <br />
????????????$proSum -= $proCur; <br />
????????} <br />
????} <br />
????unset ($proArr); <br />
????return $result; <br />
}