Unable to initialize module的php错误的原因通常是因为模块和php的版本不一致导致的。例如下面错误：

[[email protected]]# php -v
PHP Warning:  PHP Startup: mhash: Unable to initialize module
Module compiled with module API=20050922, debug=0, thread-safety=0
PHP    compiled with module API=20060613, debug=0, thread-safety=0
These options need to match
 in Unknown on line 0
PHP 5.2.17 (cli) (built: Feb 19 2011 11:52:47)
Copyright (c) 1997-2010 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2010 Zend Technologies
    with Zend Extension Manager v1.2.2, Copyright (c) 2003-2007, by Zend Technologies
    with Zend Optimizer v3.3.3, Copyright (c) 1998-2007, by Zend Technologies
[[email protected]]# yum list installed | grep php-mhash
php-mhash.i386                              5.1.6-15.el5.centos.1      installed

明显，mhash模块版本5.1.6和php的版本5.2.17不一致

解决办法，吧mhash模块升级到对应的php版本

[[email protected]]#  yum --enablerepo=webtatic --exclude=php*5.3* update -y php-mhash
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror.steadfast.net
 * extras: mirrors.gigenet.com
 * updates: mirror.ubiquityservers.com
webtatic                                                                                                                                                  |  951 B     00:00    
webtatic/primary                                                                                                                                          |  42 kB     00:00    
webtatic                                                                                                                                                                 229/229
Excluding Packages in global exclude list
Finished
Setting up Update Process
Resolving Dependencies
--> Running transaction check
---> Package php-mhash.i386 0:5.2.17-1.1.w5 set to be updated
--> Finished Dependency Resolution

Dependencies Resolved

=================================================================================================================================================================================
 Package                                    Arch                                  Version                                        Repository                                 Size
=================================================================================================================================================================================
Updating:
 php-mhash                                  i386                                  5.2.17-1.1.w5                                  webtatic                                   20 k

Transaction Summary
=================================================================================================================================================================================
Install       0 Package(s)
Upgrade       1 Package(s)

Total download size: 20 k
Downloading Packages:
php-mhash-5.2.17-1.1.w5.i386.rpm                                                                                                                          |  20 kB     00:00    
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Updating       : php-mhash                                                                                                                                                 1/2
  Cleanup        : php-mhash                                                                                                                                                 2/2

Updated:
  php-mhash.i386 0:5.2.17-1.1.w5                                                                                                                                                

Complete!