Interleaving of local variables and global variables in PHP (1) Variables in nested for loops

I believe that many students who come from c++/java/c# may make such mistakes:

<?php
  for($i=0;$i<9;$i++)
{
    #some code
    #many many code!...
    for($i=0;$i<8;$i++)
     {
          #some my ugly code
      }
}
?>

There is a big for loop outside. After writing a lot of code, another loop is needed. Everyone thinks I don’t want to throw another i, we do this in other languages, but after doing this in PHP, you will find that the code becomes an infinite loop! What is the reason?

It turns out that the for statement is not a function, but a form of statement. In php, both i are treated as global variables. Every time the loop inside is run, i is reassigned to 7, of course forever. There is no way to break out of the cycle.

My solution is to try to separate the names of the auto-incrementing variables in each for loop, which can greatly avoid this problem. And try to use foreach.

The above introduces the interleaving of local variables and global variables in PHP (1) Variables in nested for loops, including aspects of the content. I hope it will be helpful to friends who are interested in PHP tutorials.