Without loops at all? Can't be done. Without you having to write the loop? Explode or one of the regex "split" methods.

Without you actually doing the looping part, something based on array_map + explode should do the trick ; for instance, considering you are using PHP 5.3 :

$str = "A,5|B,3|C,8";

$a = array_map(
    function ($substr) {
        return explode(',', $substr);
    }, 
    explode('|', $str)
);
var_dump($a);

Will get you :

array
  0 => 
    array
      0 => string 'A' (length=1)
      1 => string '5' (length=1)
  1 => 
    array
      0 => string 'B' (length=1)
      1 => string '3' (length=1)
  2 => 
    array
      0 => string 'C' (length=1)
      1 => string '8' (length=1)

Of course, this portion of code could be re-written to not use a lambda-function, and work with PHP < 5.3 -- but not as fun ^^

Still, I presume array_map will loop over each element of the array returned by explode... So, even if the loop is not in your code, there will still be one...

preg_match_all("~([^|,]+),([^|,]+)~", $str, $m);
$result = array_combine($m[1], $m[2]);

this returns an array like array('A' => 5, 'B' => 3 etc

You can use a combination of map and explode, but you're not really avoiding a loop, you're just not using for/while statements.

http://php.net/manual/en/function.array-map.php

If your data is huge this could get heavy but here's one solution:

<?php
$data = "A,5|B,3|C,8";
$search = array("|",",");
$replace = array("&","=");
$array = parse_str(str_replace($search, $replace, $data));
?>

Would result into something like this:

$array = array(
  A => 5,
  B => 3,
  C => 8,
);

Depending on whether array_walk() counts as a loop...

<?php

class Splitter {  
  function __construct($text){
    $this->items = array();
    array_walk(explode('|', $text), array($this, 'split'));
  }

  function split($input){
    $this->items[] = explode(',', $input);
  }
}

$s = new Splitter("A,5|B,3|C,8");
print_r($s->items);

A small loop would be best.

$array1 = split('|',$data);
$final=array();
$foreach($array1 as $arraypart) {
$part = split(',',$arraypart);
$final[$part[0]] = $part[1];
}