Using select on eloquent model causes "Undefined offset:0" - php

Question

I am new to laravel. I have written code like below. And when I add select, it causes an error saying undefined offset: 0.
It also causes same error when I have more than two records even though I commented out select part.
When I check the query using toSql(), it is perfectly fine.
So when I use dd() on $clientDrivers before return, the output is below. (Seems fine as well)
What would be the problem with my code?
Any suggestion or advice would be appreicated.
EDIT: I have found the problem which was the $appends in Driver Model. Why does $appends cause the problem?
Solution: I have fixed my Driver Model getBankAttribute which is used for $appends and it works fine.
Here is my code:
Model
public function drivers() {
return $this->belongsToMany('App\Model\User\Driver', 'ClientDriver', 'client_id', 'userdriver_id');
}
Controller
$client = ClientModel::findOrFail($id);
$select = ['UserDriver.name as userdriver_name', 'UserDriver.phone_number as userdriver_phone_number'];
$clientDrivers = $client->drivers()
->select($select) // this does not work. If this is commented out it works perfectly fine.
->get();
return response($clientDrivers, 200);
Result of dd($clientDrivers)
Collection {#805
#items: array:2 [
0 => Driver {#798
#dates: array:1 [
0 => "deleted_time"
]
#table: "UserDriver"
+timestamps: false
+appends: array:1 [
0 => "bank"
]
#connection: "mysql"
#primaryKey: "id"
#keyType: "int"
+incrementing: true
#with: []
#withCount: []
#perPage: 15
+exists: true
+wasRecentlyCreated: false
#attributes: array:2 [
"userdriver_name" => "driver1"
"userdriver_phone_number" => "140412351235"
]
#original: array:4 [
"userdriver_name" => "driver1"
"userdriver_phone_number" => "140412351235"
"pivot_client_id" => 1
"pivot_userdriver_id" => 1
]
#changes: []
#casts: []
#dateFormat: null
#dispatchesEvents: []
#observables: []
#relations: array:1 [
"pivot" => Pivot {#801
+pivotParent: Client {#713
#table: "Client"
#guarded: array:2 [
0 => "id"
1 => "created_time"
]
#connection: "mysql"
#primaryKey: "id"
#keyType: "int"
+incrementing: true
#with: []
#withCount: []
#perPage: 15
+exists: true
+wasRecentlyCreated: false
#attributes: array:20 [
"id" => 1
"created_time" => "2017-12-28 05:23:50"
"invoice_email" => ""
"biz_number" => "1234512345"
]
#original: array:20 [
"id" => 1
"created_time" => "2017-12-28 05:23:50"
"invoice_email" => ""
"biz_number" => "1234512345"
]
#changes: []
#casts: []
#dates: []
#dateFormat: null
#appends: []
#dispatchesEvents: []
#observables: []
#relations: []
#touches: []
+timestamps: true
#hidden: []
#visible: []
#fillable: []
#forceDeleting: false
}
#foreignKey: "client_id"
#relatedKey: "userdriver_id"
#guarded: []
#connection: "mysql"
#table: "ClientDriver"
#primaryKey: "id"
#keyType: "int"
+incrementing: true
#with: []
#withCount: []
#perPage: 15
+exists: true
+wasRecentlyCreated: false
#attributes: array:2 [
"client_id" => 1
"userdriver_id" => 1
]
#original: array:2 [
"client_id" => 1
"userdriver_id" => 1
]
#changes: []
#casts: []
#dates: []
#dateFormat: null
#appends: []
#dispatchesEvents: []
#observables: []
#relations: []
#touches: []
+timestamps: false
#hidden: []
#visible: []
#fillable: []
}
]
#touches: []
#hidden: []
#visible: []
#fillable: []
#guarded: array:1 [
0 => "*"
]
#rememberTokenName: "remember_token"
}
1 => Driver {#799
#dates: array:1 [
0 => "deleted_time"
]
#table: "UserDriver"
+timestamps: false
+appends: array:1 [
0 => "bank"
]
#connection: "mysql"
#primaryKey: "id"
#keyType: "int"
+incrementing: true
#with: []
#withCount: []
#perPage: 15
+exists: true
+wasRecentlyCreated: false
#attributes: array:2 [
"userdriver_name" => "driver2"
"userdriver_phone_number" => "140412351236"
]
#original: array:4 [
"userdriver_name" => "driver2"
"userdriver_phone_number" => "140412351236"
"pivot_client_id" => 1
"pivot_userdriver_id" => 2
]
#changes: []
#casts: []
#dateFormat: null
#dispatchesEvents: []
#observables: []
#relations: array:1 [
"pivot" => Pivot {#803
+pivotParent: Client {#713}
#foreignKey: "client_id"
#relatedKey: "userdriver_id"
#guarded: []
#connection: "mysql"
#table: "ClientDriver"
#primaryKey: "id"
#keyType: "int"
+incrementing: true
#with: []
#withCount: []
#perPage: 15
+exists: true
+wasRecentlyCreated: false
#attributes: array:2 [
"client_id" => 1
"userdriver_id" => 2
]
#original: array:2 [
"client_id" => 1
"userdriver_id" => 2
]
#changes: []
#casts: []
#dates: []
#dateFormat: null
#appends: []
#dispatchesEvents: []
#observables: []
#relations: []
#touches: []
+timestamps: false
#hidden: []
#visible: []
#fillable: []
}
]
#touches: []
#hidden: []
#visible: []
#fillable: []
#guarded: array:1 [
0 => "*"
]
#rememberTokenName: "remember_token"
}
]
}

Answer 1

You need to pass string in $select. You are currently passing array in it.
Change your $select as below:
$select = "'UserDriver.name as userdriver_name', 'UserDriver.phone_number as userdriver_phone_number'";

Answer 2

You could use with() to get associated drivers for a client
$client = ClientModel::where('id',$id)
->with('drivers:name,phone_number')
->get();
$clientDrivers = $client->drivers;
return response($clientDrivers, 200);