Symfony 5 :Relation ManyToMany do not save - php

Question

in my project i create 2 entities :Projects & category.They are a ManyToMany relation MySql shema
im using Easy-admin bundle trying to Manage my database but the problem is when i try to add a category to a project it will not save, it work when i try to add a project to a category but i don't know why it fails in the other way . thanks for help :)
Category
<?php
namespace App\Entity;
use App\Repository\CategoryRepository;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity(repositoryClass=CategoryRepository::class)
* #ORM\Table(name="category")
*/
class Category
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
*/
private $id;
/**
* #ORM\Column(type="string", length=255)
*/
private $title;
/**
* #ORM\Column(type="text")
*/
private $body;
/**
* #ORM\Column(type="string", length=255)
*/
private $image;
/**
* #ORM\Column(type="datetime")
*/
private $createdAt;
/**
* #ORM\ManyToMany(targetEntity=Projects::class, inversedBy="category",cascade={"persist"})
*
*/
private $projects;
public function __construct()
{
$this->projects = new ArrayCollection();
}
public function getId(): ?int
{
return $this->id;
}
public function getTitle(): ?string
{
return $this->title;
}
public function setTitle(string $title): self
{
$this->title = $title;
return $this;
}
public function getBody(): ?string
{
return $this->body;
}
public function setBody(string $body): self
{
$this->body = $body;
return $this;
}
public function getImage(): ?string
{
return $this->image;
}
public function setImage(string $image): self
{
$this->image = $image;
return $this;
}
public function getCreatedAt(): ?\DateTimeInterface
{
return $this->createdAt;
}
public function setCreatedAt(\DateTimeInterface $createdAt): self
{
$this->createdAt = $createdAt;
return $this;
}
/**
* #return Collection|projects[]
*/
public function getProjects(): Collection
{
return $this->projects;
}
public function addProjects(projects $project): self
{
if (!$this->projects->contains($project)) {
$this->projects[] = $project;
$project->addCategory($this);
}
return $this;
}
public function removeProjects(projects $project): self
{
if ($this->projects->contains($project)) {
$this->projects->removeElement($project);
$project->removeCategory($this);
}
return $this;
}
public function __toString()
{
return $this->title;
}
}
projects
<?php
namespace App\Entity;
use App\Repository\ProjectsRepository;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity(repositoryClass=ProjectsRepository::class)
* #ORM\Table(name="projects")
*/
class Projects
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
*/
private $id;
/**
* #ORM\Column(type="string", length=255)
*/
private $title;
/**
*
* #ORM\Column(type="text")
*/
private $body;
/**
* #ORM\Column(type="string", length=255)
*/
private $image;
/**
* #ORM\Column(type="datetime")
*/
private $createdAt;
/**
* #ORM\ManyToMany(targetEntity=Category::class, mappedBy="projects",cascade={"persist"})
*/
private $category;
public function __construct()
{
$this->category = new ArrayCollection();
}
public function getId(): ?int
{
return $this->id;
}
public function getTitle(): ?string
{
return $this->title;
}
public function setTitle(string $title): self
{
$this->title = $title;
return $this;
}
public function getBody(): ?string
{
return $this->body;
}
public function setBody(string $body): self
{
$this->body = $body;
return $this;
}
public function getImage(): ?string
{
return $this->image;
}
public function setImage(string $image): self
{
$this->image = $image;
return $this;
}
public function getCreatedAt(): ?\DateTimeInterface
{
return $this->createdAt;
}
public function setCreatedAt(\DateTimeInterface $createdAt): self
{
$this->createdAt = $createdAt;
return $this;
}
/**
* #return Collection|category
*/
public function getCategory(): Collection
{
return $this->category;
}
public function addCategory(category $category): self
{
if (!$this->category->contains($category)) {
$this->category[] = $category;
$category->addProjects($this);
}
return $this;
}
public function removeCategory(Category $category): self
{
if ($this->category->contains($category)) {
$this->category->removeElement($category);
$category->removeProjects($this);
}
return $this;
}
public function __toString()
{
return $this->title;
}
}

Answer 1

I suspect, that the adders and removers are never called. In the case of Category::getProjects you return the collection, which, when changed, will lead to updates in the database, since it's the owning side of the relation.
On the other side however, you got Projects::getCategory, which also returns the collection, which probably is modified, but the changes are not propagated to the database at all, since it's the inverse side.
To fix this, I presume you have to fix your pluralization:
Category's property should be called $projects, the getter should be called getProjects and imho return $this->projects->toArray(); (the implementation details should be hidden), the adder should be named addProject (note the missing s) and the remover removeProject. Symfony will handle the different pluralizations and understand which methods to call.
the class should be called Project (no plural s) and similarly the getters, adders and removers have their names getCategories, addCategory and removeCategory. again, in the getter return $this->categories->toArray(). providing the collection might lead to the bundle editing the collection directly, especially if the adders and removers are named weirdly.
After these changes (adapting the #ManyToMany annotations too of course), it should work (tm).

Answer 2

it worked the mapping was false it should be like this in
category
#ORM\ManyToMany(targetEntity=Projects::class, mappedBy="categories")
and like this in projects
#ORM\ManyToMany(targetEntity=Category::class, inversedBy="projects")
then i droped the db and update the schema ... plus the fix of the pluralization
thnx a lot <3 <3