PHP基本不了解一些代码？

I am struggling understanding how this code works. when we call the function with a value 5, the value of c, becomes 5. Now 5 + 25 = 30 . What i don't understand is how the value of the $_GET['c'] equals to 25, when it should be 5.

my answer would therefore be 5 + 25 - 5 - 10 = 15.

<?php
   function process($c, $d = 25){
     global $e;
     $retval = $c + $d - $_GET['c'] - $e;
     return $retval;
   }

   $e = 10;
   echo process(5);
?>

Its variables should be getting another value, maybe you use "global" you might be picking up the value from another location.

Try show variables:

<?php
   function process($c, $d = 25){
     global $e;

     echo '$e: ', $e , '<br>';
     echo '$c: ', $c , '<br>';
     echo '$d: ', $d , '<br>';
     echo '$_GET['c']: ', $_GET['c'] , '<br>';

     $retval = $c + $d - $_GET['c'] - $e;

     echo $c ,' + ' , $d , ' - ' , $_GET['c'] , ' - ' , $e , ' = ' , $retval , '<hr>';

     return $retval;
   }

   $e = 10;
   echo process(5);
?>

So you will probably find the variable problem.

In some cases you can use a static function in a class (php object oriented)