php issue with looping over an array twice using foreach and passing value by reference
When you execute a foreach loop, the variables in the () persist after the loop is done. That means that after the first loop finishes, you can var_dump($v) and get the values that were contained in it after the last iteration through the first loop. This is the case whether it's a reference (&$v) or a normal variable ($v).
However, if it's a reference in the first loop, it remains a reference unless it's unset. That means when you enter the second loop, you're overwriting the reference with the value of the array element you're currently looking at.
Remember, what foreach($cases as $k => $v) really means is "take the key for this element in $cases and assign that to $k, and take the value for this element and assign it to $v)". Since $v is still a reference to the last element in the array, rather than setting the value of a new variable $v, you're actually updating the value of where $v already points to.
What that means is, if we simplify $cases to be simply ['a', 'b', 'c', 'd'], after the first time through the second foreach, $cases is now ['a', 'b', 'c', 'a'] because you've reassigned the element in $cases that $v points to - the last one - to have the same value as the first one. The second time through, it's ['a', 'b', 'c', 'b']. The third time through it's ['a', 'b', 'c', 'c']. Then, the last time through, you're assigning it to itself, and at that time it holds the value 'c'.
This is really just a case of php working as expected. The solution is to unset($v) as soon as the first loop finishes, to make sure that the next time you use $v you're using a new variable, rather than an existing reference.
To see this in action:
Head on over to http://phpfiddle.org/ and paste the following code, and run it; you'll see in the output that $v is maintained after the first loop completes, and that the value of $cases[5] changes each time through the second loop.
$cases = array( array('caseStyle' => 'case style 1', 'caseNum' => 'case01'), array('caseStyle' => 'case style 2', 'caseNum' => 'case02'), array('caseStyle' => 'case style 3', 'caseNum' => 'case03'), array('caseStyle' => 'case style 4', 'caseNum' => 'case04'), array('caseStyle' => 'case style 5', 'caseNum' => 'case05'), array('caseStyle' => 'case style 6', 'caseNum' => 'case06'));foreach ($cases as $k => &$v) { $v['caseNum'] = ucwords($v['caseNum']);}var_dump($v);echo "<br />";foreach ($cases as $k => $v) { print_r($cases); echo "<br />"; echo $k . ': ' . $v['caseNum'] . ' - ' . $v['caseStyle'] . '<br/>';}