Define Variable in Function to use GLOBALLY

Need to define a variable within a function, but you'd like to use it throughout your script..... here is an example on how to create it and how you can use it.

 <?php  
 ///  how to define a variable in a function to use globals  
 function myCode(){  
   $GLOBALS['magic'] = "what";       
 }  
 myCode(); /// -- run function   
 echo $magic; //<-- OUTPUT WHAT.  
 function test(){  
      echo $GLOBALS['magic'];  /// <-- output What  
 };  
 ?>