Removing related entity Symfony2 - symfony

Question

I have related entities. Many to Many relation and the annotation exists on only one entity:
/**
* #ORM\ManyToMany(targetEntity="Event")
* #ORM\JoinTable(name="viewed_events",
* joinColumns={#ORM\JoinColumn(name="user_id", referencedColumnName="id")},
* inverseJoinColumns={#ORM\JoinColumn(name="event_id", referencedColumnName="id")}
* )
**/
protected $viewedEvents;
The problem is when I try to delete Event entity I get Integrity constraint violation: 1451 Cannot delete or update a parent row: a foreign key constraint fails error. How do I solve this? I tried adding orphanRemoval=true like that: #ORM\ManyToMany(targetEntity="Event", orphanRemoval=true) and also tried adding cascade="delete" and cascade="all" instead with no success.

Answer 1

I give you one simple example so that you can work out what you need to add/change in your application.
Assume that there is a M-N relationship between Student and Course entities.
STUDENT
class Student
{
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
/**
* #ORM\OneToMany(targetEntity="StudentCourse", mappedBy="studentInverse", cascade={"persist", "remove"})
*/
protected $studentInverse;
public function __construct()
{
$this->studentInverse = new \Doctrine\Common\Collections\ArrayCollection();
}
}
COURSE
class Course
{
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
/**
* #ORM\OneToMany(targetEntity="StudentCourse", mappedBy="courseMap", cascade={"persist", "remove"})
*/
protected $courseInverse;
public function __construct()
{
$this->courseInverse = new \Doctrine\Common\Collections\ArrayCollection();
}
}
STUDENTCOURSE (this the one you're more interested in)
class StudentCourse
{
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
/**
* #ORM\ManyToOne(targetEntity="Course", inversedBy="courseInverse")
* #ORM\JoinColumn(name="course", referencedColumnName="id", nullable=false, onDelete="CASCADE")
*/
protected $courseMap;
/**
* #ORM\ManyToOne(targetEntity="Student", inversedBy="studentInverse")
* #ORM\JoinColumn(name="student", referencedColumnName="id", nullable=false, onDelete="CASCADE")
*/
protected $studentMap;
}

Answer 2

onDelete="CASCADE"
On Yours JoinColumn.