Doctrine inserting error - File languages.php

<?php
namespace models;

/**
 * @Entity
 * @Table(name="languages")
 */
class Languages {
    /**
     * @Id
     * @Column(name="id", type="integer", nullable=false)
     * @GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @Column(type="string", length="255", nullable=false)
     */
    protected $title;

    /**
     * @Column(type="string", length="255", nullable=false)
     */
    protected $slug;

    /**
     * @Column(type="string", length="255", nullable=false)
     */
    protected $icon;



    /* Setters & Getters */
    public function setIcon($icon){ $this->icon = $icon; }
    public function getIcon(){ return $this->icon; }

    public function setSlug($slug){ $this->slug = $slug; }
    public function getSlug(){ return $this->slug; }

    public function setTitle($title){ $this->title = $title; }
    public function getTitle(){ return $this->title; }
}