We can discuss much more about our experience being together gether with PHP.
PHP Performance and the solutions we can discuss here.
3. if u have lots of concurrent access and u r using php session with files session handler, u should consider to use at least 1 level deep of session folder by configuring your php.ini like this and manually create the required folder:
session.save_handler = files
session.save_path = "1;/tmp/sessionfolder"
inside /tmp/sessionfolder create folder from a-z,A-Z,0-9
instead of having file based native ext3/ext4 (linux) filesystem, why not put all you session in RAM/Memory.
to add some more spice to it add additional OS layer tip by using ram based filesystem such as tmpfs (linux/bsd/sun - syntax may differ):
manually creating it using mount command:
# mount -t tmpfs -o size=100m,mode=0755 tmpfs /tmp/sessionfolder
or just at it in your /etc/fstab add this line:
tmpfs /tmp/sessionfolder cache tmpfs size=100M,mode=0755 0 0
mount -a # to mount it without rebooting your machine
Php Hip Hop ni pun nampak menarik tapi belum try lagi. https://github.com/facebook/hiphop-php/wiki
hiphop dari fb 
Too basics but helpful...
I saw some programmer practice commenting html which has embedded php codes.
Sample:
<p>
College List
</p>
<p>
echo listAllCollege();
</p>
<!--<p>
School List
</p>
<p>
echo listAllSchool();
</p> -->Writing above code might be fine for development env. but not in production. If you did that, please ViewSource and you will the commented lists.
mana php tag?
Few tips on PHP tuning (not code tuning)
1. having a byte code cache can give a huge performance boost - APC
2. output_handler = ob_gzhandler in php ini file, will reduce your apache load and transmission time, especially for large output from php interpretor... resulting significant less OS load, and increase apache concurrency performance...
akan di tambah lagi bila ada masa...