isset() does not seem to work on an array

Question

I am working on an existing piece of PHP code and try to understand it in order to debug an issue:

echo "Got here !!!\n";
var_dump($aHeaders);
if (isset($aHeaders['SALESCHANNEL'])) {
    echo "aHeaders['SALESCHANNEL'] is set\n";
    ...
} elseif (isset($aHeaders['SALESUNIT'])) {
    echo "aHeaders['SALESUNIT'] is set\n";
    ...
}
echo "Got there !!!\n";

and I get the following output:

Got here !!!
array(1) {  
 ["EMAIL,FIRSTNAME,LASTNAME,PHONE,TITLE,DATEOFBIRTH,SALESUNIT,LANGUAGE,STATUS,IS_RESELLER,CUSTOMDATE,ADDRESS_1,ADDRESS_2,CITY,COUNTRY,ZIPCODE,"]=>
int(0) }
Got there !!!

I am no deep expert at PHP, but I believe I should see:

aHeaders['SALESUNIT'] is set

in the output. What is going wrong?

My PHP version is PHP 5.5.30 if it matters.

Answer 1

What you currently have is this:

$arr1 = array('EMAIL,FIRSTNAME,LASTNAME,PHONE,TITLE,DATEOFBIRTH,SALESUNIT,LANGUAGE,STATUS');

isset() would only work if you have the following:

$arr2 = array(
    'EMAIL' => 'blah',
    'FIRSTNAME' => 'blah',
    'LASTNAME' => 'blah',
    'PHONE' => 'blah',
    'TITLE' => 'blah',
    'DATEOFBIRTH' => 'blah',
    'SALESUNIT' => 'blah',
    'LANGUAGE' => 'blah',
    'STATUS' => 'blah'
);