使用array_diff()，如何从array2而不是array1中获取差异?

I'm trying to use array_diff like so. Here are my two array outputs:

列表 1 输出

Array ([0] => 0022806 ) 

列表 2 输出

Array ([0] => 0022806 [1] => 0023199 ) 

PHP

$diff = array_diff($list_1, $list_2);

print "DIFF: " . count($diff) ."<br>";
print_r($diff);

输出是:

DIFF: 0
Array ( )

知道我做错了什么吗?为什么没有返回0023199?