Here is the solution that ultimately worked for me in getting the session_save.path to becoming listed as writeable in the pre-installation window of Joomla during a manual installation. My site is hosted by Host Monster.
These are the steps I followed:
1) I first went to the root directory of my site and looked for a file entitled “tmp”. I found the file and made sure the permissions were set to 777.
2) Using my ftp program, FileZilla, I then made a new file in my local directory and called it “phpinfo.php”. I then opened the file on my computer to insert a simple line of code which is:
<?
php phpinfo();
?>
I then saved the file and uploaded it to my public html directory on my server.
3) I then opened my browser window and in the address line typed in:
Note: that you would insert the name of your site in place of “mywebsite” in the above address.
This will generate a PHP Settings report in your browser window. Search on this page for "session.save_path". Read the value which is assigned to it. Mine stated NO VALUE
4) I then went back to my FTP program FileZilla, I downloaded a copy of the “php.ini” to my local site. I then edited the file in order to assign the session.save_path. I searched the file text for “session.save_path. Once located in the text, I deleted the “;” which was typed in before the session.save_path listing.
I then edited the path so that it stated the following:
session.save_path = /tmp
I then saved the php.ini file and then went back to my ftp program, FileZilla and upload it to the public file and which overwrote the old one.
Also you will need to upload the php.ini file to the Joomla sub-directory “installation”. For me this was the same folder which also contained the file called globals.php.
5) Having located the “globals.php” file in the Joomla Installation directory, I then downloaded a copy of it to my local site. I opened the file to edit it as well by inserting this line at the top of the code, after "<? php" :
ini_set('session.save_path','/path to root/tmp');
I then uploaded the file using my ftp program FileZilla which overwrote the old “globals.php” file.
6) I then restarted the Joomla manual installation and the pre-installation showed a “Green” light. The session.save_path was Writeable and showed it was set to “/tmp”.
I hope this helps, it took me days to find the right combination of steps.