foreach loop scope with multidimensional arrays - php

Question

Can someone explain the output of this code?
Why is it "fb" instead of "100100"?
$items = array();
$items[] = "foo";
$items[] = "bar";
foreach($items as $item) {
$item['points'] = 100;
}
foreach($items as $item) {
echo $item['points']; //output: "fb"
}

Answer 1

You loop though the $items array, which has two elements.
First: foo and second: bar. E.g.
Array (
[0] => foo
[1] => bar
)
Now you access them like this:
echo $item['points'];
PHP will convert points which is a string into an integer, as you can see from the manual warning:
Warning: [...] Non-integer types are converted to integer. [...]
Which in your case will be 0.
And so you access the two values (strings) as array:
string: f o o
index: 0 1 2 //$index["points"] -> $index[0]
string: b a r
index: 0 1 2 //$index["points"] -> $index[0]
So you print the first character of both strings (e.g. foo and bar), which are:
fb
EDIT:
Also worth to note here is, that PHP only silently converts it with PHP <5.4 from newer version you will get a warning, as from the manual:
As of PHP 5.4 string offsets have to either be integers or integer-like strings, otherwise a warning will be thrown. Previously an offset like "foo" was silently cast to 0.
Which in your case with PHP >=5.4 you would get:
Warning: Illegal string offset 'points' ...

Answer 2

I found this question intriguing.
I had my own walk-through and here is the result.
$items is defined as follows.
$items = [
0 => "foo",
1 => "bar"
];
Then, goes into the foreach loop.
foreach($items as $item) {
$item['points'] = 100;
}
At the beginning, $item contains a string "foo". The [] syntax is dominantly used for associative arrays, so it tricks us that $item might be an array, which is not the case. A less well-known usage of the [] is to get/set a single character in a string via [int] or {int} expression, as #Rizier123 has noted in his answer. For example, a "string"[0] gives "s". So, the following code
$item['points'] = 100;
is virtually similar to
"foo"['points'] = 100;
Now, a non-integer value given as a character position of a string, raises a PHP warning, and the position (here 'points') will be force-converted to an integer.
// Converting a string to integer:
echo intval('points'); // gives 0
As a result, the "foo"['points']" statement becomes "foo"[0], so
"foo"[0] = 100;
Now, the assignment part. The [] syntax operates on a single character. The numeric 100 is first converted to a string "100" and then only the first character is taken out for the assignment operation(=). The expression is now similar to
"foo"[0] = "1"; // result: "1oo"
To make things a bit twisted, the modified value of $item( which is "1oo") is not preserved. It's because the $item is not a reference. See https://stackoverflow.com/a/9920684/760211 for more information.
So, all the previous operations are negligible in terms of the end result. The $items are intact in the original state.
Now, in the last loop, we can see that the $item['point'] statement tries to read a character out of a string, in an erroneous way.
foreach($items as $item) {
echo $item['points']; //output: "fb"
}
echo "foo"[0]; // "f"
echo "boo"[0]; // "b"

Answer 3

You're not actually modifying the array by doing $items as $item. $item is its own variable, so it would make sense that you get the correct output when printing within that loop.