常用资源
判断是否为空
+--------------+-----------+---------+-----------+---------+--------+
| 真值表 | gettype() | empty() | is_null() | isset() | (bool) |
+--------------+-----------+---------+-----------+---------+--------+
| $x = "" | string | true | false | true | false |
| $x=null | NULL | true | true | false | false |
| var $x | NULL | true | true | false | false |
| $x = array() | array | true | false | true | false |
| $x = false | boolean | true | false | true | false |
| $x = 15 | integer | false | false | true | true |
| $x = 1 | integer | false | false | true | true |
| $x = 0 | integer | true | false | true | false |
| $x = -1 | integer | false | false | true | true |
| $x = '15' | string | false | false | true | true |
| $x = '1' | string | false | false | true | true |
| $x = '0' | string | true | false | true | false |
| $x = '-1' | string | false | false | true | true |
| $x = 'foo' | string | false | false | true | true |
| $x = 'true' | string | false | false | true | true |
| $x = 'false' | string | false | false | true | true |
+--------------+-----------+---------+-----------+---------+--------+
常用代码
页面编码
header("Content-type: text/html; charset=utf-8");
去除数组中的键名，保留值
$array = array_values($array);
