This question is an exact duplicate of:
PHP version upgrade to 5.5.10 will cause any problem to my existing magento 1.5 application?
Please help me.
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You may need to rollback your php version to 5.5 to 5.3 or 5.2 or need to apply magento patch because magento not worked correctly on newer version of php and there are some known issues. Magento patches for some issues are available and some of them are still pending. For more details you can go through with this nice post http://www.whitefirdesign.com/blog/2013/12/10/using-magento-with-php-5-4-and-5-5/