Not Understanding the Difference/Similarities Between a Key and an Array Index...

Hi, in PHP they are the same thing, the index is a key to the values stored against each number. I've never though of it that way until watching this video. The one thing about PHP is that your 'indexed' array may contain 5 values stored against the numbers '(0,1,2,3,4)'.

$basic = array(0,1,2,3,4);
echo var_dump($basic);
// ==> array(5) { [0]=> int(0) [1]=> int(1) [2]=> int(2) [3]=> int(3) [4]=> int(4) }

When you do a 'var_dump' you can see that they have the key definition (surrounded in []) pointing to the values.

If you unset two from the middle without 're-indexing' your index numbers may now be '(0,1,4)', which makes me think of them more as 'keys'.

unset($basic[2]);
unset($basic[3]);
echo var_dump($basic);
// ==> array(3) { [0]=> int(0) [1]=> int(1) [4]=> int(4) }

You can see in the above example that removing item '2' and '3', leaves '4' at position '4'. In other languages, removing index '2' & '3' would change '4' to position '2'. But because PHP stores them as key/value pairs, it stays as previously defined. You can reindex the array numerically by using 'array_values'.

// $basic = array_values($basic);

You can see the keys clearer if you add your own 'key' value to the same array structure to have keys '(0,1,4,"month")'.

$basic['month'] = 'June';
echo var_dump($basic);
// ==> array(4) { [0]=> int(0) [1]=> int(1) [4]=> int(4) ["month"]=> string(4) "June" }

"Key-Value" pairs is the generic way of storing data, think of variables, database data etc. If you are only using 'indexed' arrays (ie starting at '0' and going from there) then calling them indexes makes sense, but adding 'keys' into it changes it from just 'index'.

Hope this clears it up a bit.

Think of a file cabinet that has any number of drawers, and each drawer has a different lock. To get the content of a drawer, you need you use the key for that particular drawer otherwise, you can't retrieve its contents. It's basically the same concept with why array indices are called keys. You need to use the particular "key" to access that specific content (value) in the array. I hope that made sense.

Thanks for the answer :]