What does [] mean when reading from a PHP array?
I've been writing a parser for PHP and while messing around with some third-party code, I run into a weird case regarding the [] operator.
Normally, [] is used without a key on the left side of an assignment meaning "add as the last element".
$a = array();
$a[] = 1;
will add 1 in the end of array $a.
In the aforementioned code though, I saw a line like this:
$r =& $a[];
When I tried to remove the &, I got a rather expected fatal error:
Fatal error: Cannot use [] for reading
With the & though, PHP does not complain at all. What is the meaning of the expression
& $a[];
?
The syntax means "use a reference to $a[]" or a reference to the newest created array element.
<?php
$a=array( );
$a[] = "a";
$a[] = "b";
print_r($a);
$r =& $a[];
print_r($a);
$r = "c";
print_r($a);
produces:
Array
(
[0] => a
[1] => b
)
Array
(
[0] => a
[1] => b
[2] =>
)
Array
(
[0] => a
[1] => b
[2] => c
)
My guess is that it adds an empty element to the array and gives $ra reference to that array element. Are you sure $a is supposed to be an array? It could also be trying to access a character of a string using the [] syntax, in which case I have no idea how that would work.
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