Help me understand the difference between the following codes in PHP

Ok so for the first one:

<?php

$flavors = array("Cake Batter","Cookie Dough");
foreach ($flavors as $a => $b) {

//looping through values
echo $b;
exit;
}
?>

You will echo out: Cake Batter

And the second one:

<?php

$flavors = array("Cake Batter","Cookie Dough");
foreach ($flavors as $a => $b) {

//looping through keys
echo $a;
exit;
}
?>

You will echo out: 0

The reason for this is because arrays automatically store every Value along with a Key like this key => value

So the array looks like this:

$flavors = array();

$flavors[0] = "Cake Batter";
$flavors[1] = "Cookie Dough";

So 0 is the key and the value of that is Cake Batter and 1 is also a key with the value of Cookie Dough. So in the foreach loop you looped through the keys and value of the $flavors array.

The first one printed out Cake Batter because $b is the Values in the array (Cake Batter and Cookie Dough) and it said

echo $b;
exit;

So the reason why it did not print out Cookie Dough as well is because of the exit; which will cut off the loop after it loops through once which was only able to get the first value of Cake Batter.

Now for the second one it printed out 0 because it said

echo $a;
exit;

and $a in the foreach loop is representing the keys of [0] and [1]. So you looped through the keys and out putted them, but again the only reason that it only output the first key of [0] is because of the exit; which stopped the loop from running twice and just grabbed the first key of [0] and not the second key of [1].

So basically without the exit; it would loop through and output both keys and both values.

Just remember:

foreach ($flavors as $keys => $values) {
// loop
}