child element Floating parent element does not automatically adjust height problem

We know that elements are floating or relatively positioned, leaving the element out of the flow of the document. If the parent element does not set a fixed height, the height of the floating child element is not calculated when the height is calculated. However, sometimes we need the parent element to calculate the height of all its child elements (including floating elements) to adjust its own width, so as to adjust its own background border, and so on, only need to add CSS properties to the parent element: overflow:auto; zoom:1;

The parent element automatically calculates the height of all child elements within a floating child element to adjust its height.

child element Floating parent element does not automatically adjust height problem