Move array element up one place PHP

Question

I need help figuring out how to move a array item up one place using PHP. The PHP so far is as follows:

<?php
$task_list = array();
$task_list[] = 'Write chapter';
$task_list[] = 'Edit chapter';
$task_list[] = 'Proofread chapter';

switch( $_POST['action'] ) {
   case 'Promote Task':
//This is where I'm stuck.
?>

and the HTML:

<?php if (count($task_list) > 0 && empty($task_to_modify)) : ?>
<h2>Select Task:</h2>
<form action="." method="post" >
    <?php foreach( $task_list as $task ) : ?>
      <input type="hidden" name="tasklist[]" value="<?php echo $task; ?>"/>
    <?php endforeach; ?>
    <label>Task:</label>
    <select name="taskid">
        <?php foreach( $task_list as $id => $task ) : ?>
            <option value="<?php echo $id; ?>">
                <?php echo $task; ?>
            </option>
        <?php endforeach; ?>
    </select>
    <br />
    <label>&nbsp;</label>
    <input type="submit" name="action" value="Modify Task"/>
    <input type="submit" name="action" value="Promote Task"/>
    <input type="submit" name="action" value="Delete Task"/>

Any help would be much appreciated!

Answer 1

You only need to swap two rows (the selected task, and the task above). So if your indexes always are 0, 1, 2, 3, .., n:

$selectedRow = $_POST['taskid'];
if ($selectedRow === 0) {
    echo 'Already top-priority';
} else {
    $rowAbove = $taks_list[$selectedRow - 1];
    $task_list[$selectedRow - 1] = $taks_list[$selectedRow];
    $task_list[$selectedRow] = $rowAbove;

    // Or without help-variable, but less readable
    list($task_list[$selectedRow - 1], $task_list[$selectedRow])
        = array($task_list[$selectedRow], $task_list[$selectedRow - 1]);
}