PHP |向上或向下移动（键，值）对的程序

给定一个包含键值对的数组，我们需要使用键将特定值向上或向下移动。

例子：

Input : $continents = array(
                      'First' => 'Asia',
                      'Second' => 'Europe',
                      'Third' => 'North America',
                      'Fourth' => 'South America',
                            );
        move_to_up($continents, 'Third');
Output : Array
(
    [Third] => North America
    [First] => Asia
    [Second] => Europe
    [Fourth] => South America
)

Input :$continents = array(
                      'First' => 'Asia',
                      'Second' => 'Europe',
                      'Third' => 'North America',
                      'Fourth' => 'South America',
                            );
       move_to_bottom($continents, 'Second');
Output : Array
(
    [First] => Asia
    [Third] => North America
    [Fourth] => South America
    [Second] => Europe
)

使用下面描述的PHP函数可以解决上述问题：
unset() ：函数销毁指定的变量。

方法：我们准备一个带有指定键的临时数组（值要上移或下移），然后取消设置键，最后根据将值上移或下移的目的附加。

下面是方法的实现
代码 1：移动键，值在顶部

 'Asia',
                      'Second' => 'Europe',
                      'Third' => 'North America',
                      'Fourth' => 'South America',
                            );
         
        move_to_up($continents, 'Third');
        print_r ($continents);
  
function move_to_up(&$continents, $string)
       {
           $var = array($string => $continents[$string]);
           unset($continents[$string]);
           $continents = $var + $continents;
       }
?>

输出：

Array
(
    [Third] => North America
    [First] => Asia
    [Second] => Europe
    [Fourth] => South America
)

代码2：移动键，底部的值

 'Asia',
                      'Second' => 'Europe',
                      'Third' => 'North America',
                      'Fourth' => 'South America',
                            );
       move_to_bottom($continents, 'Second');
       print_r ($continents);
  
 function move_to_bottom(&$continents, $string)
       {
           $var = array($string => $continents[$string]);
           unset($continents[$string]);
           $continents = $continents + $var;
       }
         
?>

输出：

Array
(
    [First] => Asia
    [Third] => North America
    [Fourth] => South America
    [Second] => Europe
)