PHP does have autovivification, but only on write operations.

<?php

$arr = array();
$arr[0]['a'][1]['b'] = 2;
print_r($arr);

$other = array();
if ($other[0]['a'][1]['b'] == 2)
{
    die;
}
else
{
    # Note that autovivification has not happened.
    print_r($other);
}

[download]

Versus:

#!/usr/bin/env perl

use strict;
use Data::Dumper;

my @arr;
$arr[0]{'a'}[1]{'b'} = 2;
print Dumper \@arr;

my @other;
if ($other[0]{'a'}[1]{'b'} == 2)
{
    die;
}
else
{
    # Note that autovivification has happened!
    print Dumper \@other;
}

[download]

For the purposes of autovivification, ++ is considered a write operation.

The Perl module autovivification allows you to have approximately the PHP behaviour:

no autovivification;

[download]
use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

In reply to Re^2: Initializing Hash Arrays in Perl by tobyink
in thread Initializing Hash Arrays in Perl by winterwind

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