Get the key value of the last element of the array

Today, in a scenario, you need to get the maximum key value of an array,

For example:

$arr = array(

    11 => 1,

     6  => 2,

     9  => 5,

     21 => 1

);

If you want to get 21, then you have to

$maxKey = 0;

foreach( $arr as $k => $v ) {

    if( $k > $maxKey ) {

        $maxKey = $k;

    }

}

I thought this was more troublesome, but later I checked the information and found that this is also possible. ,

ksort( $arr );

end( $arr );

echo key( $arr );

That is, after k sorting, use end to point the pointer to the last element of the array, and then output the key of the array.

There is also this way, reverse the array, and then get the maximum value, but this will change the array

echo max( array_flip($arr) );

Of course, there is also this way, first get all the keys, and then get the largest key

$keys = array_keys($arr);

echo max($keys);

As for which one is better. . . It has not been tested yet