Create different range arrays from one big one - php

Question

I have an array that contains other arrays of US colleges broken down by the first letter of the alphabet. I've setup a test page so that you can see the array using print_r. That page is:
http://apps.richardmethod.com/Prehealth/Newpublic/test.php
In order to create that array, I used the following code:
$alphabetized = array();
foreach (range('A', 'Z') as $letter) {
// create new array based on letter
$alphabetized[$letter] = array();
// loop through results and add to array
foreach ( $users as $user ) {
$firstletter = substr($user->Schoolname, 0, 1);
if ( $letter == $firstletter ) {
array_unshift( $alphabetized[$letter], $user );
}
}
}
Now, I want to split the array so that a certain range of letters is in each array. For example,
arrayABCEFGH - would contain the schools that begin with the letters A, B, C, D, E, F, G, and H.
My question is, should I modify the code above so that I achieve this before I do one big array, OR should I do it after?
And here is the big question . . if so, how? :-)
Thanks in advance for any help. It's greatly appreciated.

Answer 1

First off, the code to generate the array can be made easier by only iteratating over $users:
$alphabetized = array();
// loop through results and add to array
foreach ($users as $user) {
$firstletter = strtoupper($user->Schoolname[0]);
$alphabetized[$firstletter][] = $user;
}
// sort by first letter (optional)
ksort($alphabetized);
To retrieve the first 8 entries you could use array_slice:
array_slice($alphabetized, 0, 8);
Assuming that all first letters are actually used and you used ksort() on the full array that also gives you from A - H. Otherwise you have to use array_intersect_key() and the flipped range of letters you wish to query on.
array_intersect_key($alphabetized, array_flip(range('A', 'H')));

Answer 2

If you don't need a full copy of the array, then you should encapsulate the above code in a function that has an array as its argument ($letterRange), which will hold the specific array identifiers (letters) to be in the final array.
Then you would need to encapsulate the code within the foreach using an if block:
if (in_array($letter, $letterRange)) { ... }
This would result in an array only containing the letter arrays for the specified letters in $letterRange.

Answer 3

You could write a simple function that takes an array, and an array of keys to extract from that array, and returns an array containing just those keys and their values. A sort of array_slice for non-numeric keys:
function values_at($array, $keys) {
return array_intersect_key($array, array_flip($keys));
}
Which you can then call like this to get what you want out of your alphabetized list:
$arrayABCDEFGH = values_at($alphabetized, range('A','H'));