想要按键的值对数组进行排序，但在web中找不到解决方案。
我想在PHP中按键is_paid对这个数组DESC进行排序，所以FROM原始数组：
[user_courses] => Array
(
[1] => Array
(
[paid_course_id] => 1
[course_name] => english
[course_label] => English
[is_paid] => 1
[time] => 1378925144
[voucher] => 0
)
[2] => Array
(
[paid_course_id] => 2
[course_name] => spanish
[course_label] => English
[is_paid] => 0
[time] => 1379073137
[voucher] => 0
)
[3] => Array
(
[paid_course_id] => 3
[course_name] => russian
[course_label] => Russian
[is_paid] => 1
[time] => 1452277777
[voucher] => 0
)
)
成为：
[user_courses] => Array
(
[1] => Array
(
[paid_course_id] => 1
[course_name] => english
[course_label] => English
[is_paid] => 1
[time] => 1378925144
[voucher] => 0
)
[3] => Array
(
[paid_course_id] => 3
[course_name] => russian
[course_label] => Russian
[is_paid] => 1
[time] => 1452277777
[voucher] => 0
)
[2] => Array
(
[paid_course_id] => 2
[course_name] => spanish
[course_label] => English
[is_paid] => 0
[time] => 1379073137
[voucher] => 0
)
)
因此，首先列出数组中is_paid为1的所有项，并在数组底部放置is_paid 0
function sortOrder($a, $b) {
return $a['paid_course_id'] > $b['paid_course_id'];
}
usort($courseArray['user_courses'], 'sortOrder');
或具有匿名功能
usort($courseArray['user_courses'], function($a, $b) {
return $a['paid_course_id'] > $b['paid_course_id'];
});