问PHP有自动生动的功能吗？

EN

// Works as you have assigned a value of 'hello'
$a['a'][4][6]['b'] = "hello";
var_dump($a);
echo print_r($a,true);

// works as you have assigned a value of 'world'
$b[][][][] = "world";
var_dump($b);
echo print_r($b,true);

// ERROR: Cannot use [] for reading
$c[];
var_dump($c);
echo print_r($c,true);

   use strict;
   use warnings;
   use Data::Dumper;

   my %a;       # as is empty, equivalent to \%a is {};
   print Dumper %a;
   $a{b}{c}{d}; # \%a is now { b => { c => {}}}
                # returns an undef value.
   print Dumper \%a;

$VAR1 = {};
$VAR1 = {
          'b' => {
                   'c' => {}
                 }
        };

use strict;
use warnings;
use Data::Dumper;

my (@b,@c);          # @b=(), @c=()
print Dumper \@b;
$b[3];               # @b=() aka unchanged.
print Dumper \@b;
$b[3][2][1];         # @b=(undef,undef,undef,[undef,undef,[]])
print Dumper \@b;
print Dumper \@c;
$c[3]=1  ;           # @c=(undef,undef,undef,1)
print Dumper \@c;

Useless use of array element in void context at -e line 7.
Useless use of array element in void context at -e line 9.
$VAR1 = [];
$VAR1 = [];
$VAR1 = [
          undef,
          undef,
          undef,
          [
            undef,
            undef,
            []
          ]
        ];
$VAR1 = [];
$VAR1 = [
          undef,
          undef,
          undef,
          1
        ];