Controller.php

		
$em = $this->getEntityManager();

$viewing = new Viewing();
$viewing->setMeetingPerson('t');
$viewing->setMeetingPlace('t');
$viewing->setContactNumber('1');
$viewing->setViewingAt(new \DateTime());

$lmo = new LeadMatchingOffice();
$lmo->addViewing($viewing);
$lmo->setDistanceMiles(1);
$viewing->setLeadMatchingOffice($lmo);

$em->persist($lmo);
$em->flush();

$em->remove($lmo);
$em->flush();

LeadMatchingOffice.php

Phoenix\CRMBundle\Entity\LeadMatchingOffice:
    type: entity
    table: lead_matching_office

    id:
        id:
            type: integer
            generator: { strategy: AUTO }

    fields:
        ...

    oneToMany:
        viewings:
            targetEntity: Phoenix\CRMBundle\Entity\Viewing
            mappedBy: lead_matching_office
            cascade: [persist, delete]

Output

SQLSTATE[23000]: Integrity constraint violation: 1451 Cannot delete or update a parent row: a foreign key constraint fails (`phoenix`.`viewing`, CONSTRAINT `FK_F5BB46989B12193B` FOREIGN KEY (`lead_matching_office_id`) REFERENCES `lead_matching_office` (`id`))

Viewing.php

Phoenix\CRMBundle\Entity\Viewing:
    type: entity
    table: viewing

    id:
        id:
            type: integer
            generator: { strategy: AUTO }

    fields:
        ...

    manyToOne:
        lead_matching_office:
            targetEntity: Phoenix\CRMBundle\Entity\LeadMatchingOffice