Divide = 0;
RegEx check for AgentType1 in Charge Code:
 Divide++;
 Set This-AgentType-Gets-Return;
RegEx check for AgentType2 in Charge Code:
 Devide++;
 Set This-AgentType-Gets-Return;
... etc ...

$valid_codes = array('A', 'J', 'L');

// deal with the special A2 case first, to get it out of the string
// this code could be generalized if more special cases need to be handled
if (stripos($charge_code, 'A2') !== FALSE)
{
	$found['J'] = true;
	str_ireplace('A2', '', $charge_code);
}

foreach ($valid_codes as $code)
{
	if (stripos($charge_code, $code) !== FALSE) // if the code was in the string
	{
		$found[$code] = true;
	}
}

<input type="hidden" name="agent[]" value="A" />

$divide = count($_POST["agent"]);
foreach($_POST["agent"] as $agent) {
    $sum = $_POST["amount"] / $divide;

    //do other stuff
}

^([A-Z]d*)*$