1.implode() 函数返回由数组元素组合成的字符串
（explode 将字符串打散为数组）
2.array_intersect_key 找出重复key值的数组重新组成新数组
$a1 = array("a"=>"r","b"=>"g","c"=>"b");
$a2 = array("a"=>"r","c"=>"d","d"=>"p");
$result = array_intersect_key($a1, $a2);
print_r($result);
输出：
Array ( [a] => r [c] => b )