sort()就地排序(即修改数组本身AKA $schools变量通过引用传递),因此不返回任何数组.但是返回一个布尔值以确定排序是否成功.
bool sort(array&$ array [,int $ sort_flags = SORT_REGULAR])
$schools = "high*low*other*";
$schools = explode("*", $schools);
sort($schools);
echo $schools[0];
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