数组自定义排序

//首先定定义一个数组保存学生信息
$arr=array(
array('no'=>1,'name'=>'zhangsan','height'=>174,'age'=>17),
array('no'=>2,'name'=>'lisi','height'=>172,'age'=>19),
array('no'=>3,'name'=>'wangwu','height'=>168,'age'=>22),
array('no'=>5,'name'=>'zhaoliu','height'=>184,'age'=>18),
array('no'=>4,'name'=>'lijun','height'=>174,'age'=>15),
);

//自定义排序函数
function cmp($a,$b){
if($a['height']!=$b['height']) return $a['height']-$b['height'];
return -($a['age']-$b['age']);
}
//调用usort对学生进行排序
usort($arr,"cmp");
var_dump($arr);

array(5) {
[0]=>
array(4) {
["no"]=>
int(3)
["name"]=>
string(6) "wangwu"
["height"]=>
int(168)
["age"]=>
int(22)
}
[1]=>
array(4) {
["no"]=>
int(2)
["name"]=>
string(4) "lisi"
["height"]=>
int(172)
["age"]=>
int(19)
}
[2]=>
array(4) {
["no"]=>
int(1)
["name"]=>
string(8) "zhangsan"
["height"]=>
int(174)
["age"]=>
int(17)
}
[3]=>
array(4) {
["no"]=>
int(4)
["name"]=>
string(5) "lijun"
["height"]=>
int(174)
["age"]=>
int(15)
}
[4]=>
array(4) {
["no"]=>
int(5)
["name"]=>
string(7) "zhaoliu"
["height"]=>
int(184)
["age"]=>
int(18)
}
}