Yii Relations error Trying to get property of non-object - php

Question

I have Cinema table & City table and I have relation with this tables by id.. and when I echo results i have PHP notice "Trying to get property of non-object"
What is the problem ? or I missed something ??
My Code:
Cinema model
public function relations()
{
// NOTE: you may need to adjust the relation name and the related
// class name for the relations automatically generated below.
return array(
'countryCode' => array(self::BELONGS_TO, 'TblCountry', 'country_code'),
'city' => array(self::BELONGS_TO, 'TblCity', 'city_id'),
'tblCinemaMovies' => array(self::HAS_MANY, 'TblCinemaMovies', 'cinema_id'),
'tblDays' => array(self::HAS_MANY, 'TblDay', 'cinema_id'),
'tblShowtimes' => array(self::HAS_MANY, 'TblShowtime', 'cinema_id'),
);
}
City model
public function relations()
{
// NOTE: you may need to adjust the relation name and the related
// class name for the relations automatically generated below.
return array(
'tblCinemas' => array(self::HAS_MANY, 'TblCinema', 'city_id'),
'countryCode' => array(self::BELONGS_TO, 'TblCountry', 'country_code'),
);
}
View file:
<?php echo $model->city_id->name; ?>

Answer 1

I recommend you to always check if the relation does not return null or an empty array.
The following code works well with HAS_ONE and BELONGS_TO relationship types:
$cinema = Cinema::model()->find(); // get a cinema instance, assuming there is at least one row in the database.
$city = $cinema->city; // get the relation
if ($city !== null) {
// $city is a valid model
} else {
// $city is null, the corresponding row does not exist in the database
}
You may also make this check without using a new variable (in this case, $city):
if ($cinema->city!==null) {
// the relation is available
}
Checking if the relation does not return null is the best way to avoid the PHP error "trying to get property of non-object". Also, if you are stuck with similar errors, it is recommended to use functions like var_dump() or, even better, a debugger.
Also, notice that array keys in the array returned from relations() function is the property that has to be accessed to get the relation model(s):
public function relations() {
return array(
'city' => array( ... ),
// city is the property that has to be accessed
// Yii's conventions recommend to use 'city_id' for the foreign key column name
);
}
Also note that it is good to follow Yii's conventions for naming relationships and columns to avoid using the same name for both a property and a relations - in this case, the relation will be unavailable and probably an error like "trying to access property of a non-object" will pop up when playing with the relation.
The last thing, when working with HAS_MANY or MANY_TO_MANY relationships, the relation returns an array of models even if there is only one model available and an empty array if there is nothing available.
Explanation in the docs:
http://www.yiiframework.com/doc/guide/1.1/en/database.arr#performing-relational-query

Answer 2

<?php echo $model->city->name; ?>
You must use $model->city to get the corresponding city of the $model.

Answer 3

Because the city_id is a array, in your view file, you should write the code like this
<?php echo $model->city_id[0]->name; ?>

Answer 4

That error happens when city_id is emptied or nulled (or the value doesn't exist in the foreign table).
If you're not sure that "city_id" exists, you can check it like this:
CHtml::value($model, 'city.name');
That way you always ensure that you'll not have an Exception when the value is empty or clear