/* 数组的常用函数
 *
 * 数组的排序函数
 *   sort()
 *   rsort()
 *   usort()
 *   asort()
 *   arsort()
 *   uasort()
 *   ksort()
 *   krsort()
 *   uksort()
 *   uatsort()
 *   natcasesort()
 *   array_multisort()
 *
 *    1.简单的数组排序
 *      sort() rsort()
 *    2.根据键名对数组排序
 *      ksort() krsort()
 *    3.根据元素的值对数组排序
 *      asort() arsort()
 *    4.根据"自然数排序“法对数组排序
 *      natsort()//区分大小写字母比较 natcasescort()//不区分大小写字母的比较
 *    5.根据用户自定义规则对数组排序
 *      usort() uasort() uksort()对键排序
 *    6.对维数组的排序
 *      array_multisort()
 *
 * 拆分、合并、分解、接合的数组函数
 *    1.array_slice()
 *    2.array_splice()//删除
 *    3.array_combine()//合并
 *    4.array_merge();//合并
 *    5.array_intersect();//多个数组的交集
 *    6.array_diff();//返回多个数组的差集
 *
 * 数组与数据结构的函数
 *   1.使用数组实现堆栈 //先进后出
 *    array_push() array_pop()
 *   2.使用数组实现队列 //先进先出
 *    array_unshift() array_shift() unset()
 *
 * 
 * 其他与数组操作有关的函数
 *    array_rand()
 *    shuffle()
 *    array_sum()
 *    range()
 */

//简单数组排序的使用
$data=array(5,8,1,7,2);
sort($data);//元素由小到大进行排序
print_r($data);//Array ( [0] => 1 [1] => 2 [2] => 5 [3] => 7 [4] => 8 )
rsort($data);//元素由大到小进行排序
print_r($data);//Array ( [0] => 8 [1] => 7 [2] => 5 [3] => 2 [4] => 1 )

//根据键名排序的例子
$data_2=array(5=>"five",8=>"eight",1=>"one",7=>"seven",2=>"two");
ksort($data_2);//对数组的下标进行由小到大排序
print_r($data_2);//Array ( [1] => one [2] => two [5] => five [7] => seven [8] => eight )
krsort($data_2);//对数组的下标进行由大到小排序
print_r($data_2);//Array ( [8] => eight [7] => seven [5] => five [2] => two [1] => one )

 

//根据元素的值对数组排序
$data_3=array("1"=>"Linux","a"=>"Apache","m"=>"MySQL","l"=>"PHP");
//asort() arsort  与 sort() rsort()的区别在于 前者排序后保持原有的键名,后者不保持原有键名，且键名从0开始
asort($data_3);
print_r($data_3);//Array ( [a] => Apache [1] => Linux [m] => MySQL [l] => PHP )
echo '
';
arsort($data_3);
print_r($data_3);//Array ( [l] => PHP [m] => MySQL [1] => Linux [a] => Apache )
echo '
';
sort($data_3);
print_r($data_3);//Array ( [0] => Apache [1] => Linux [2] => MySQL [3] => PHP )
echo '
';
rsort($data_3);
print_r($data_3);//Array ( [0] => PHP [1] => MySQL [2] => Linux [3] => Apache )

//根据”自然数排序法“对数组排序(0-9短者优先)
$data_4=array("file.txt","file11.txt","file2.txt","file22.txt");
sort($data_4);
print_r($data_4);//Array ( [0] => file.txt [1] => file11.txt [2] => file2.txt [3] => file22.txt )
echo '
';
natsort($data_4);
print_r($data_4);//Array ( [0] => file.txt [2] => file2.txt [1] => file11.txt [3] => file22.txt )
echo '
';
natcasesort($data_4);
print_r($data_4);//Array ( [0] => file.txt [2] => file2.txt [1] => file11.txt [3] => file22.txt )
echo '
';

//用户自定义排序函数
echo '
';
$data_5=array("Linux","Apache","MySQL","PHP");
usort($data_5,"sortbylen");//通过元素长度排序
print_r($data_5);//Array ( [0] => PHP [1] => MySQL [2] => Linux [3] => Apache )
function sortbylen($one,$two){
 if(strlen($one)==strlen($two))
  return 0;
 else
  return (strlen($one)>strlen($two))?1:-1;
}