Laravel Eloquent - One to Many - Can't join - php

Question

I'm using laravel 5.4, have two models ParentAccount and ChildAccount,
A parent has many childs
Parent
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class ParentAccount extends Model
{
//
public $timestamps = false;
protected $table = 'parent_accounts';
protected $fillable = [
'name', 'account_id'
];
public function childs()
{
return $this->hasMany('App\ChildAccount','account_id', 'parent_id');
}
}
child
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class ChildAccount extends Model
{
//
public $timestamps = false;
protected $table = 'child_accounts';
protected $fillable = [
'name', 'account_id','parent_id'
];
}
When i use echo ParentAccount::find(1)->childs();
i get an error Call to a member function childs() on null although all parents have children
Note: child has parent_id where it's the account_id in the parent

Answer 1

in parent model
public function childs(){
return $this->hasMany(ChildAccount::class, 'parent_id' , 'account_id');
}
in child model
public function parent(){
return $this->belongsTo(ParentAccount::class, 'parent_id' , 'account_id');

Answer 2

Edited Code
public function childs()
{
return $this->hasMany('App\ChildAccount', 'parent_id','account_id');
}
The relation function must be in the format
public function post()
{
return $this->belongsTo('App\Post', 'foreign_key', 'other_key');
}

Answer 3

First you have to add the primaryKey property then change the relation parameters and add the revers relation to the ChildAccount :
ParentAccount :
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class ParentAccount extends Model
{
protected $primaryKey = 'account_id';
public $timestamps = false;
protected $table = 'parent_accounts';
protected $fillable = [
'name', 'account_id'
];
public function childs()
{
// 'foreign_key', 'local_key'
return $this->hasMany('App\ChildAccount', 'parent_id', 'account_id');
}
}
ChildAccount :
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class ChildAccount extends Model
{
protected $primaryKey = 'account_id';
public $timestamps = false;
protected $table = 'child_accounts';
protected $fillable = [
'name', 'account_id','parent_id'
];
public function parent() {
// foreign_key, 'other_key'
return $this->belongsTo('App\ParentAccount', 'parent_id', 'account_id');
}
}
With doing that you can get the childs :
ParentAccount::find(1)->childs;

Answer 4

You got Call to a member function childs() on null because ParentAccount::find(1) return null. Make sure you have ParentAccount with id=1 in your DB.
You need to change keys order like this:
public function childs()
{
return $this->hasMany('App\ChildAccount', 'parent_id', 'account_id');
}