Can't find the error behind the undefined index - php

Question

I have the following code, and i keep getting undefined index error, the code is failing on test5() but i'm unable to find the error.
<?php
function test1() {
$vars = [0, 1, 2, 4, 3];
for ($i = 0; $i < count($vars); $i++) {
print $vars[$i] . "\n";
}
}
function test2() {
$flavors = ['vanilla', 'pistachio', 'banana', 'caramel', 'strawberry'];
$favorite = 'banana';
foreach ($flavors as $key => $flavor) {
if ($flavor === $favorite) {
print $key . "\n";
break;
}
}
}
function test3() {
$stuff = ['shoes', 33, null, false, true];
$selected = 0;
foreach ($stuff as $key => $thing) {
if ($thing == $selected) {
print $key . "\n";
break;
}
}
}
function test4() {
$four = 4;
$five = test4_helper($four);
print "four: $four\n";
print "five: $five\n";
}
function test4_helper(&$arg) {
$return = $arg++;
return $return;
}
function test5() {
$products = [
'Trek Fuel EX 8' => [
'price' => 2000,
'quantity' => 1
],
'Trek Remedy 9' => [
'price' => 2600,
'quantity' => 2
],
'Trek Scratch 8' => [
'price' => 3500,
'quantity' => 1
]
];
$total = 0;
$callback = function ($product, $name) {
//$total = 0;
$tax = 1.2;
$price = $product[$name]['price'];
$total += ($price * $product[$name]['quantity']) * $tax;
return $total;
};
array_walk($products, $callback);
print "$total\n";
}
/* * **********************************
* *** DO NOT EDIT BELOW THIS LINE ****
* *********************************** */
$tests = 5;
for ($i = 1; $i <= $tests; $i++) {
$function = "test$i";
print "\n\n==== Test $i ====\n";
$function();
print "==== END of test $i ====\n <br>";
}
what is the problem with this code?
it looks that it's failing on test 5

Answer 1

PHP closures are not like JavaScript ones in that they do not inherit the parent scope. You need to pass in any dependencies via the use construct. In your example...
$callback = function ($product, $name) use ($total) {
// etc
See http://php.net/manual/functions.anonymous.php#example-166

Answer 2

Arrays in PHP are defined like this:
$products = array(
'Trek Fuel EX 8' => array(
'price' => 2000,
'quantity' => 1
),
'Trek Remedy 9' => array(
'price' => 2600,
'quantity' => 2
),
'Trek Scratch 8' => array(
'price' => 3500,
'quantity' => 1
)
);
Which means you also need to look at $vars = [0, 1, 2, 4, 3]; and $flavors = ['vanilla', 'pistachio', 'banana', 'caramel', 'strawberry']; and fix them too.