Undefined offset: 0 with PHP array - php

Question

I have the following code in my Symfony 2 web project in one of my repositories:
$result = $qb->getQuery()->getResult();
$converted = $this->transformArray($result);
return $converted[0];
My problem:
I get the following error which points to the last line:
Notice: Undefined offset: 0
Background:
My function transformArray() does the following:
private function transformArray($rows)
{
foreach ($rows as $i => $row) {
$rows[$i]['hexcolor'] = $this->convertColor($row['colorR'], $row['colorG'], $row['colorB']);
};
return $rows;
}
After this operation, my variable $converted contains an array like this with only one result:
array (
0 =>
array (
'subjectId' => 1234,
'subjectName' => 'English',
'hexcolor' => '#ff00'
)
)
Can anyone explain why doing $converted[0] (= trying to access the 0 index) results in an undefined offset error? Pasting the array output into a PHPFiddle and trying to access the 0 index works totally fine. How come it does not in my Symfony 2 project?

Answer 1

This is where going a little extra Mile with your code comes in handy. By that, it is meant something so simple as adding a few extra lines of code like so:
<?php
$result = $qb->getQuery()->getResult();
// DOES THE QUERY EVEN RETURN ANY RESULTS?
// IF NOT, SET $converted TO EMPTY ARRAY: WHY NOT?
$converted = (!empty($result)) ? $this->transformArray($result) : array();
// RETURN $converted[0] ONLY IF IT EXISTS, OTHERWISE NULL
return isset($converted[0]) ? $converted[0] : null;