Install this plugin into your CakePHP application using composer:

composer require admad/cakephp-sequence

Then load the plugin by running CLI command:

./bin/cake plugin load ADmad/Sequence

SequenceBehavior provided by this plugin maintains a contiguous sequence of integers in a selected column, for records in a table records (optionally with grouping) when adding, editing (including moving groups) or deleting records.

Add the SequenceBehavior for your table and viola:

$this->addBehavior('ADmad/Sequence.Sequence');

You can customize various options as shown:

$this->addBehavior('ADmad/Sequence.Sequence', [
    'sequenceField' => 'position', // Field to use to store integer sequence. Default "position".
    'scope' => ['group_id'], // Array of field names to use for grouping records. Default [].
    'startAt' => 1, // Initial value for sequence. Default 1.
]);

Now whenever to add a new record its position field will be automatically set to current largest value in sequence plus one.

When editing records you can set the position to a new value and the position of other records in the list will be automatically updated to maintain proper sequence.

When doing a find on the table an order clause is automatically added to the query to order by the position field if a order clause has not already been set.

Move up record by one position:

$modelObject->moveUp($entity);

Move down record by one position:

$modelObject->moveDown($entity);

Set order for list of records provided. Records can be provided as array of entities or array of associative arrays like [['id' => 1], ['id' => 2]] or array of primary key values like [1, 2].

Shout out to @neilcrookes for his wonderful Sequence Behavior for CakePHP 1.3 which was the inspiration for this plugin.