framework/helpers/BaseHtml.php
public static function cssStyleFromArray(array $style)
    {
        $result = '';
        foreach ($style as $name => $value) {
            $result .= "$name: $value; ";
        }
        // return null if empty to avoid rendering the "style" attribute
        return $result === '' ? null : rtrim($result);
    }
public static function cssStyleFromArray(array $style)
    {
        $result = '';
        foreach ($style as $name => $value) {
            $result .= "$name: $value; ";
        }
        // return null if empty to avoid rendering the "style" attribute
        return $result === '' ? null : rtrim($result);
    }
Converts a CSS style array into a string representation.

For example,

```php
print_r(Html::cssStyleFromArray(['width' => '100px', 'height' => '200px']));
// will display: 'width: 100px; height: 200px;'
```

@param array $style the CSS style array. The array keys are the CSS property names,
and the array values are the corresponding CSS property values.
@return string the CSS style string. If the CSS style is empty, a null will be returned.