Check file input on PHP and JQuery. Why Error?

For Web Development
Methods onClick and onMouseMove in html code are very easy to use. Let’s also consider the events of clicking and hovering the mouse over an element for the Java Script and jQuery programming languages.
If you want your ad not to be hidden when scrolling through the site page. This algorithm shows the block when it scrolls off the screen.
How do I select an element inside the this construct? How does this jquery work?
You can create tags in any container. The new tag can be placed at the beginning or end of the parent tag. You can use the Java Script or JQuery commands.
A well thought out menu is an accordion for your website. Simple code, classic design.
A convenient and easy way to display a tooltip when you hover over a tag. Just add attribute data-tooltip and class sp_que.
How to get the values of the INPUT tag by id, class and name, using jQuery or Java Script.