gistfile1.php

<?php
/*
Increase or decrease value in CakePHP with little footprint.
 
Add this to your AppModel.
 
Usage:
(in Controller)
 
$this->Model->increase('field_name', 1);
 
(in Model)
$this->decrease('field_name', 10);
 
*/
 
/**
 * Updates a specific field with a given value
 *
 * @param $field Field name to update
 * @param $value The step to use to increase the $field
 * @return mixed
 */
private function _change($field, $value, $sign) {
 
	$schema = $this->schema();
 
	if( ! isset( $schema[$field] ) ) {
		throw new Exception("No such field: " . $field, 1);
	}
 
	if( ! in_array( $sign, array('+', '-') ) ) {
		throw new Exception("Not a valid mathematic sign", 1);
	}
 
	$sql = "UPDATE `" . $this->table . "` SET `" . $field . "` = `" . $field . "` " . $sign . " ? WHERE `" . $this->primaryKey . "` = ? LIMIT 1";
	$result = $this->query($sql, array( $value, $this->id));
 
	return $result;
}
 
/**
 * Increase a specific $field with a given $value
 *
 * @param $field Field name to update
 * @param $value The step to use to increase the $field
 * @return mixed
 */
public function decrease($field, $value) {
 
	return $this->_change($field, $value, '-');
}
 
/**
 * Decrease a specific $field with a given $value
 *
 * @param $field Field name to update
 * @param $value The step to use to increase the $field
 * @return mixed
 */
public function increase($field, $value) {
 
	return $this->_change($field, $value, '+');
}

Good approach, thanks !