Optimize, 200-500 line ish PHP scripts for memory efficiency etc..

Hello,

I'm looking for an EXPERIENCED developer with a knowledge of PHP and preferably SQL access technologies, i.e. PDO, MYSQLI etc..

I have developed a number of php scripts to facilitate the back end of an Android application, however it has been receiving considerable traffic and forced a move onto a VPS, it also shows that it is horrifically un-optimized and currently uses standard mysql_query etc..

The scripts simply either:

Read all values from SQL db, json encode the values then display
or
Get all DB values, delete names older than the most recent 100

Should take no longer than 2 hours for someone qualified, budgeted £15 per hour.

UK/US/Enlish speaking only please.