mysql errors after upgrading php and mysql
I added the following items to my.cnf which fixed my PDO broken pipe issues.  I am using a homebrew installation of mysql on a macbook pro with 16GB RAM:
key_buffer_size = 384M
max_allowed_packet = 100M
table_open_cache = 512
sort_buffer_size = 2M
read_buffer_size = 2M
read_rnd_buffer_size = 8M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size = 32M
query_cache_size = 128M
query_cache_size = 256M
Try number of CPU's*2 for thread_concurrency
thread_concurrency = 8
innodb_buffer_pool_size=512M