yii2 gridview count（）：参数必须是实现Countable php 7.2的数组或对象

Question

Error:

count(): Parameter must be an array or an object that implements Countable

The error comes from \\vendor\\yiisoft\\yii2\\helpers\\BaseHtml.php (line 1302)

 $content = Html::tag('tr', implode('', $cells), $this->headerRowOptions);

which calls: vendor\\yiisoft\\yii2\\helpers\\BaseHtml.php (line 150)

$html = "<$name" . static::renderTagAttributes($options) . '>'

which in turn calls:

if (count($attributes) > 1) { ...

(which is also in the same file)

The question is : what is the source of this error and how is it fixed/avoided?

The answer is included and is found below... The cause of the problem was not very intuitive.

This question was added for the sole purpose of helping others who might come across a similar problem using yii2 and upgrading to php 7.2

Answer 1

The reason for the problem in this case was that in the gridview the property 'headerRowOptions' was set by an anonymous function:

'headerRowOptions' =>  function ($model, $key, $index, $grid) {
                    return ['style' => 'vertical-align: middle !important;'];
                },

When changed to an array, the error was gone and everything worked as expected:

  'headerRowOptions' => ['style' => 'vertical-align: middle !important;'],

Hopefully this helps someone in a similar situation.