I recently tried to upgrade to php-4.0.1pl2, and the sessions does not work. The error_log : 
-------------------------------------------- 
PHP Warning: Failed to write session data. Please check that the current settin 
g of session.save_path is correct (/tmp/) in Unknown on line 0 
<br> 
<b>Warning</b>: Failed to write session data. Please check that the current set 
ting of session.save_path is correct (/tmp/) in <b>Unknown</b> on line <b>0</b>< 
br> 
------------------------------------------- 

But /tmp is the directory where php4.0.0 used to write its session data and it worked for php4.0.0 . Anyone got the same problem with php4.0.1pl2 like I do? 

    And also I tried to use "/tmp" instead of "/tmp/" and it reports the same warning... The permission on /tmp is exactly the same as it was when running php4.0.0.