是否可以使用jQuery来确定行高？

The best way to explain this is using an example:

<div style="width:100px;height:100px;overflow:hidden;">
   <?php echo $content; ?>
</div>

How can I use jQuery to see if there's text overflowing?

Compare the element's scrollHeight (DOM property, hence .get(0)) and height to check whether the contents of an element exceeds the element's boundaries or not.

var $div = $("div"); //Assume one div. Use a more specific selector
var isOverflowing = $div.get(0).scrollHeight != $div.height();
//The variable `isOverflowing` is true if the text overflows