How to do the double-layer loop operation of for

Question

Asking for code

Answer 1

Code screenshot

Screenshot of the effect after running:

I wonder if I can meet your requirements

Answer 2

What's the meaning? ?

for($i=0;$i<5;$i++)
{
echo "<br>";
for($j=0;$j<5;$j++)
{
echo $j;
}
}

Output

01234

01234

01234

01234

01234

The outer layer controls how many times the inner layer loops

Answer 3

<script>alert('你好')</script>