How to get equal parts of multiple strings/array?

-drum roll- Time for a one-liner!

$result = array_count_values(array_map(function($v) {list($a) = explode("-",$v); return $a;},$input));

(Assumes $input is your array of codes)

If you are using PHP 5.4 or newer (you should be), then:

$result = array_count_values(array_map(function($v) {return explode("-",$v)[0];},$input));

Tested in PHP CLI:

If the prefix is always followed by a '-' then you can do something like this:-

foreach ($codes as $code) {
    $tmp = explode("-",$code);
    $result[$tmp[0]] += 1;
}
print_r($result);

Depends on the variability of the data, but something like:

preg_match_all('/^([^-]+)/m', $string, $matches);
$result = array_count_values($matches[1]);

print_r($result);

If you don't know that there is an - after the prefix but the prefix is always letters then:

preg_match_all('/^([A-Z]+)/im', $string, $matches);
$result = array_count_values($matches[1]);

Otherwise you'll have to define exactly what the prefix can contain if it's not the delimiter.

Since you stated via comment to Niet that you don't have a reliable delimiter, then we can only write a pattern that identifies your targeted substrings based on their location in each line.

I recommend preg_match_all() with no capture group, a start of the line anchor, and a multi-line pattern modifier (m).

I've written a preg_split() alternative, but the pattern is a little "clunkier" because of the way I'm handling the line returns.

Code: (Demo)

$string = 'VIP-AX757
VIP-QBHE6
CODE-IUEF7
CODE-QDGF3
VIP-KJQFB';

var_export(array_count_values(preg_match_all('~^[A-Z]+~m', $string, $out) ? $out[0] : []));
echo "\n\n";
var_export(array_count_values(preg_split('~[^A-Z][^\r\n]+\R?~', $string, -1, PREG_SPLIT_NO_EMPTY)));

Output:

array (
  'VIP' => 3,
  'CODE' => 2,
)

array (
  'VIP' => 3,
  'CODE' => 2,
)