Object mapping loop

[Nexus633]

Hello, I have the following problem.

#[Entity, Table(name: 'employee')]
class Employee
{
    use IdTrait;

    #[Column(name: 'employee_number', type: 'string', length: 255, unique: false, nullable: false)]
    private string $employee_number;

    #[Column(name: 'firm_number', type: 'integer', length: 11, unique: false, nullable: true)]
    private ?int $firm_number;

    #[Column(name: 'username', type: 'string', length: 255, unique: true, nullable: false)]
    private string $username;

    #[OneToMany(targetEntity: MachineAssignment::class, mappedBy: 'employee', cascade: ["all"])]
    protected ?Collection $assignments;

    public function getEmployeeNumber(): string
    {
        return $this->employee_number;
    }

    public function setEmployeeNumber(string $employee_number): void
    {
        $this->employee_number = $employee_number;
    }

    public function getFirmNumber(): ?int
    {
        return $this->firm_number ?: 0;
    }

    public function setFirmNumber(?int $firm_number): void
    {
        $this->firm_number = $firm_number;
    }

    public function getUsername(): string
    {
        return $this->username;
    }

    public function setUsername(string $username): void
    {
        $this->username = $username;
    }

    public function getAssignments(): ?Collection
    {
        return $this->assignments;
    }

    public function setAssignments(?Collection $assignments): void
    {
        $this->assignments = $assignments;
    }

}


#[Entity, Table(name: 'machine_assignment')]
class MachineAssignment
{

    use IdTrait;

    #[Column(name: 'customer_id', type: 'integer', length: 11)]
    private int $customer_id;

    #[Column(name: 'employee_id', type: 'integer', length: 11)]
    private int $employee_id;

    #[ManyToOne(targetEntity: Customer::class, inversedBy: 'assignments')]
    #[JoinColumn(name: 'customer_id', referencedColumnName: 'id')]
    private Customer $customer;

    #[ManyToOne(targetEntity: Employee::class, inversedBy:'assignments')]
    #[JoinColumn(name: 'employee_id', referencedColumnName: 'id')]
    private Employee $employee;

    public function getFirm(): null|string
    {
        return $this->employee->getFirm();
    }

    public function setEmployee(Employee $employee): void
    {
        $this->employee = $employee;
    }

    public function getEmployee(): Employee
    {
        return $this->employee;
    }

    public function getCustomer(): Customer
    {
        return $this->customer;
    }

    public function setCustomer(Customer $customer): void
    {
        $this->customer = $customer;
    }
}

If I now call the employee, I automatically get the Assignments object. That's how it should be! However, it now constantly nests the employee with the assignment. As soon as I want to send the object as JSON via an API, everything crashes. A loop is created!
How can I prevent this?

[derrabus]

Use a serializer library such as Symfony Serializer and tell it to ignore that property.

[Nexus633]

Thank you for your answer.
I got that far too, but I think it's being ignored.

    #[ManyToOne(targetEntity: Employee::class, inversedBy:'assignments')]
    #[JoinColumn(name: 'employee_id', referencedColumnName: 'id')]
    #[Serializer\MaxDepth(1)]
    private Employee $employee;
    
    #[OneToMany(targetEntity: MachineAssignment::class, mappedBy: 'employee', cascade: ["all"])]
    #[Serializer\MaxDepth(1)]
    protected ?Collection $assignments;

I don't know what else to do. I use the JMS\Serializer.

[derrabus]

I can't help you much with JMS Serializer, I'm afraid.