意为把session存放在 "/tmp/php_sess" 目录下，并且分成 2 级子目录，每级子目录又分别有 16 个子目录。
接下来，假设php的主目录为 /usr/local/server/php/，则新建一个文件 /usr/local/server/php/include/php/ext/session/mod_files.sh，其内容如下：

#! /bin/sh
# NAME
#      mod_files.sh  - Update of the php-source/ext/session/mod_files.sh
#
# SYNOPSIS
#      mod_files.sh basedir depth [numberofsubdirs]
#
# DESCRIPTION
#      this script creates the directories tree used by php to store the session files
#      (see php.ini - 'session.save_path' option)
#
#      Example: if you want php to store the session files in a directory tree
#      of 3 levels of depth containing 32 directories in each directory,
#      first, put the setting bellow in the php.ini file:
#
#      session.save_path = "3;/tmp/session"
#
#      Now create the basedir directory: 'mkdir /tmp/session'
#
#      Then, call this scrip with the following arguments:
#
#      ./mod_files.sh ./mod_files.sh /tmp/session 3 32
if test "$2" = ""; then
       echo "usage: $0 basedir depth [numberofsubdirs]"
       echo "numberofsubdirs: if unset, defaults to 16. if 32, 32 subdirs, if 64, 64 subdirs."
       exit 1
fi
if test "$2" = "0"; then
       exit 0
fi
hash_chars="0 1 2 3 4 5 6 7 8 9 a b c d e f"
if [ ! -z $3 ] ; then
if test "$3" -a "$3" -eq "32"; then
  hash_chars="$hash_chars g h i j k l m n o p q r s t u v"
  if test "$3" -eq "64"; then
   hash_chars="$hash_chars w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z - ,"
  fi
fi
fi
for i in $hash_chars; do
       newpath="$1/$i"
       mkdir $newpath || exit 1
       sh $0 $newpath `expr $2 - 1` $3
done