Php.ini file can be found:

vim /etc/php.ini

memory_limit is the maximum amount of memory in bytes that a script is allowed to allocate.

memory_limit = 128M

upload_max_filesize is the maximum size of an uploaded file

upload_max_filesize = 2M

This value also effects file upload. To upload files this value must be 15% larger than the upload_max_filesize.

post_max_size = 8M

Once you have made changes to the file you will need to reload apache for them to take effect:

service httpd graceful