Timestampable Trait for doctrine entities to use in order to not to repeat them in individual entities.

Timestampable.php

<?php

namespace AppBundle\Entity\Traits;

use Doctrine\ORM\Mapping as ORM;

/**
 * Adds created at and updated at timestamps to entities.
 * Entities using this must have HasLifecycleCallbacks annotation.
 *
 * @ORM\HasLifecycleCallbacks
 */
trait Timestampable
{
    /**
     * @var \DateTime
     *
     * @ORM\Column(name="created_at", type="datetime")
     */
    private $createdAt;

    /**
     * @var \DateTime
     *
     * @ORM\Column(name="updated_at", type="datetime")
     */
    private $updatedAt;

    /**
     * Gets triggered only on insert
     *
     * @ORM\PrePersist
     */
    public function onPrePersist()
    {
        $this->createdAt = new \DateTime();
        $this->updatedAt = new \DateTime();
    }

    /**
     * Gets triggered every time on update
     *
     * @ORM\PreUpdate
     */
    public function onPreUpdate()
    {
        $this->updatedAt = new \DateTime();
    }

    /**
     * Set createdAt
     *
     * @param \DateTime $createdAt
     */
    public function setCreatedAt($createdAt)
    {
        $this->createdAt = $createdAt;

        return $this;
    }

    /**
     * Get createdAt
     *
     * @return \DateTime
     */
    public function getCreatedAt()
    {
        return $this->createdAt;
    }

    /**
     * Set updatedAt
     *
     * @param \DateTime $updatedAt
     */
    public function setUpdatedAt($updatedAt)
    {
        $this->updatedAt = $updatedAt;

        return $this;
    }

    /**
     * Get updatedAt
     *
     * @return \DateTime
     */
    public function getUpdatedAt()
    {
        return $this->updatedAt;
    }
}

User.php

<?php

namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use AppBundle\Entity\Traits\Timestampable;

/**
 * User
 *
 * @ORM\Table(name="user")
 * @ORM\Entity(repositoryClass="AppBundle\Repository\UserRepository")
 * 
 * @ORM\HasLifecycleCallbacks
 */
class User
{
    /*
     * Timestampable trait
     */
    use Timestampable;

    /**
     * @var int
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @var string
     *
     * @ORM\Column(name="firstname", type="string", length=64)
     */
    private $firstname;

    /**
     * @var string
     *
     * @ORM\Column(name="lastname", type="string", length=64)
     */
    private $lastname;

    /**
     * @var string
     *
     * @ORM\Column(name="email", type="string", length=255, unique=true)
     */
    private $email;

    /**
     * @var string
     *
     * @ORM\Column(name="password", type="string", length=64)
     */
    private $password;


    /**
     * Get id
     *
     * @return int
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set firstname
     *
     * @param string $firstname
     *
     * @return User
     */
    public function setFirstname($firstname)
    {
        $this->firstname = $firstname;

        return $this;
    }

    /**
     * Get firstname
     *
     * @return string
     */
    public function getFirstname()
    {
        return $this->firstname;
    }

    /**
     * Set lastname
     *
     * @param string $lastname
     *
     * @return User
     */
    public function setLastname($lastname)
    {
        $this->lastname = $lastname;

        return $this;
    }

    /**
     * Get lastname
     *
     * @return string
     */
    public function getLastname()
    {
        return $this->lastname;
    }

    /**
     * Set email
     *
     * @param string $email
     *
     * @return User
     */
    public function setEmail($email)
    {
        $this->email = $email;

        return $this;
    }

    /**
     * Get email
     *
     * @return string
     */
    public function getEmail()
    {
        return $this->email;
    }

    /**
     * Set password
     *
     * @param string $password
     *
     * @return User
     */
    public function setPassword($password)
    {
        $this->password = $password;

        return $this;
    }

    /**
     * Get password
     *
     * @return string
     */
    public function getPassword()
    {
        return $this->password;
    }
}

Maybe you need to use attributes in php8 :

<?php

namespace App\Entity\Traits;

use Doctrine\DBAL\Types\Types;
use Doctrine\ORM\Mapping as ORM;

#[ORM\HasLifecycleCallbacks]
trait Timestampable
{
    #[ORM\Column(type: Types::DATETIME_MUTABLE, nullable: true)]
    private ?\DateTimeInterface $createdAt = null;

    #[ORM\Column(type: Types::DATETIME_MUTABLE, nullable: true)]
    private ?\DateTimeInterface $updatedAt = null;

    #[ORM\PrePersist]
    public function onPrePersist(): never
    {
        $this->createdAt = new \DateTime();
        $this->updatedAt = new \DateTime();
    }

    #[ORM\PreUpdate]
    public function onPreUpdate(): never
    {
        $this->updatedAt = new \DateTime();
    }

    /**
     * @param \DateTimeInterface $createdAt
     * @return static
     */
    public function setCreatedAt(\DateTimeInterface $createdAt): static
    {
        $this->createdAt = $createdAt;

        return $this;
    }

    /**
     * @return \DateTimeInterface
     */
    public function getCreatedAt(): \DateTimeInterface
    {
        return $this->createdAt;
    }

    /**
     * @param \DateTimeInterface $updatedAt
     * @return static
     */
    public function setUpdatedAt(\DateTimeInterface $updatedAt): static
    {
        $this->updatedAt = $updatedAt;

        return $this;
    }

    /**
     * @return \DateTimeInterface
     */
    public function getUpdatedAt(): \DateTimeInterface
    {
        return $this->updatedAt;
    }
}