mysql - YII2 - Handle NULL value in gridView- Display a column of foreign keys where some may be NULL -


in brief, have table machines, has fk pointing subcategory.id relation correctly setup gii. however, fk column in machine can set null action field not compulsory.

 [     'attribute'=>'machine sub-category',     'value' => function ($model) {     return $model->subcategory->subcat_name;      },      ],

above code displays subcategory name when fk not null. if fk null, php error:

trying property of non-object

i understand error because of null value. ( because don't error if add value instead of null)

so query - fk column may have null values, how them display in gridview or detailview?

you can check if subcategory null 

[   'attribute'=>'machine sub-category',   'value' => function ($model) {     if (isset($model->subcategory)){       return $model->subcategory->subcat_name;       } else {       return '';       }    }, ],

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