PromoCode.php

/**
 * @ORM\ManyToMany(targetEntity="App\Entity\PromoCodeUsed", inversedBy="promoCodes")
 */
 private $promoCodeUsed;

 /**
 * @return Collection|PromoCodeUsed[]
 */
public function getPromoCodeUsed(): Collection
  {
        return $this->promoCodeUsed;
  }

public function addPromoCodeUsed(PromoCodeUsed $promoCodeUsed): self
  {
        if (!$this->promoCodeUsed->contains($promoCodeUsed)) {
            $this->promoCodeUsed[] = $promoCodeUsed;
  }

        return $this;
}

 public function removePromoCodeUsed(PromoCodeUsed $promoCodeUsed): self
    {
    if ($this->promoCodeUsed->contains($promoCodeUsed)) {
          $this->promoCodeUsed->removeElement($promoCodeUsed);
     }

        return $this;
 }

PromoCodeUsed.php
 /**
 * @return Collection|self[]
 */
 public function getPromoCode(): Collection
    {
        return $this->promoCode;
    }

 public function addPromoCode(self $promoCode): self
    {
        if (!$this->promoCode->contains($promoCode)) {
            $this->promoCode[] = $promoCode;
        }

        return $this;
    }

 public function removePromoCode(self $promoCode): self
    {
        if ($this->promoCode->contains($promoCode)) {
            $this->promoCode->removeElement($promoCode);
        }

        return $this;
    }