您需要爆炸 转换为实际数组:

You need to explode $schools into an actual array:

$schools = $_SESSION['sarray'];
$schools_array = explode(",", $schools);
$result = count($schools_array);

如果您只需要计数，并且100％确保它是一个干净的逗号分隔列表，则还可以使用

if you just need the count, and are 100% sure it's a clean comma separated list, you could also use substr_count() which may be marginally faster and, more importantly, easier on memory with very large sets of data:

$result = substr_count( $_SESSION['sarray'], ",") +1; 
 // add 1 if list is always a,b,c;