ordenar-csv.php

<?php

$csv = array(
    array('Jose', 'jose@tectonica.com', 'Buenos Aires, Argentina'),
    array('Albo', 'albo@pragmore.com', 'New York, USA'),
);

$_POST['columns'] = array('firstname', 'email', 'location');

$columns = $_POST['columns'];

$csvOrdered = array();
foreach ($csv as $row) {
    $rowOrdered = array();
    foreach ($columns as $position => $key) {
        $rowOrdered[$key] = $row[$position];
    }   
    $csvOrdered[] = $rowOrdered;
}
var_dump($csvOrdered);