php string function

Elegant way to extract certain words or letters from a string. Found at php.net.

 <?php  
 /* subtok(string,chr,pos,len)  
  *  
  * chr = chr used to seperate tokens  
  * pos = starting postion  
  * len = length, if negative count back from right  
  *   
  * subtok('a.b.c.d.e','.',0)   = 'a.b.c.d.e'  
  * subtok('a.b.c.d.e','.',0,2)  = 'a.b'  
  * subtok('a.b.c.d.e','.',2,1)  = 'c'  
  * subtok('a.b.c.d.e','.',2,-1) = 'c.d'  
  * subtok('a.b.c.d.e','.',-4)  = 'b.c.d.e'  
  * subtok('a.b.c.d.e','.',-4,2) = 'b.c'  
  * subtok('a.b.c.d.e','.',-4,-1) = 'b.c.d'  
  */  
 function subtok($string,$chr,$pos,$len = NULL) {  
  return implode($chr,array_slice(explode($chr,$string),$pos,$len));  
 }  
 ?>