Say you store a csv formatted string somewhere to represent an array. For example, Johnny has items “apple|orange|banana”. Then in your code, you may parse out the items as follows:

$items = "apple|orange|banana"; // retrieve it from somewhere
$my_arr = explode("|", $items);
if (count($my_arr) > 0){
  print "Johnny has something.";
}else{
  print "Johnny has nothing.";
}

It works fine as it seems.

Well, actually, you will never see the “Johnny has nothing” print out. Surprisingly, even if $items is an empty string, explode will still return an array with one element. That array is:

Array
(
  [0] =>
)

Sigh… to avoid this, if you have to use the csv format, then add an if statement to double check the string length.

$items = "apple|orange|banana"; // retrieve it from somewhere
if ($items != ""){
  $my_arr = explode("|", $items);
  print "Johnny has something.";
}else{
  print "Johnny has nothing.";
}

Best practice I think is to store such an array in json format. That way you can completely avoid this surprise!

Ref: http://www.php.net/manual/en/function.explode.php#99830

Say you wrote some code below for projectA.

function do_task(){
  // init
  my_init();
  // calling a class function
  $v = class_A::some_method($p1, $p2, $p3, $p4, $p5, $p6, $p7);
  // return
  return $v;
}

Now, your boss loves it. Then he asks you to do a very similar thing for projectB. Naively, you may do:

function do_task($project_type){
  // init
  my_init();
  // calling a class function
  if ($project_type == "projectA"){
    $v = class_A::some_method($p1, $p2, $p3, $p4, $p5, $p6, $p7);
  }elseif ($project_type == "projectB"){
    $v = class_B::some_method($p1, $p2, $p3, $p4, $p5, $p6, $p7);
  }
  // return
  return $v;
}

Um… it would work, but imagine if you will soon have projectC, and D, and on… and what if you need to add one more parameter to the some_method function?

In my opinion, the do_task function needs to be generalized, by taking in the class name as a parameter. Then add a lookup function to translate project names to class names. See below:

function do_task($class_name){
  // init
  my_init();
  // calling a class function
  $my_class = new $class_name();
  $v = $my_class::some_method($p1, $p2, $p3, $p4, $p5, $p6, $p7);
  // return
  return $v;
}

function lookup_class_name($project_name){
  switch ($project_name){
    case "projectA": return "class_A";
    case "projectB": return "class_B";
    // ...
  }
}

// main
$class_name = lookup_class_name("projectB");
$v = do_task($class_name);

The code looks a lot more manageable now. 😉

So now I assumed you already got memcache running. If not, check out my previous tutorial on how to do that.

Now in your php project, include the following code somewhere in your init.php file. Or you can always make it object oriented if you like.

# Connect to memcache:
global $memcache;
global $memcache_server_up;
$memcache = new Memcache;
$memcache_server_up = $memcache->connect('127.0.0.1', 11211);

# check to see if memcache server is up
function memcache_server_is_up(){
	global $memcache_server_up;
	return $memcache_server_up;
}

# Gets key / value pair into memcache
function getCache($key) {
	global $memcache;
	if (memcache_server_is_up()) {
		return $memcache->get($key);
	}else{
		return "";
	}
}

# Puts key / value pair into memcache
function setCache($key, &$object, $timeout = 600) {
	global $memcache;
	if (memcache_server_is_up()) {
		return $memcache->set($key,$object,MEMCACHE_COMPRESSED,$timeout);
	}
}

My setup will work if you have only one memcache daemon running. If you have a few, then make your changes accordingly.

So in your actual code, just do something like the following.

include_once "init.php";

$cache_key = "a key that uniquely identifies your object";
$obj = getCache($cache_key);
if ($obj == ""){
	$obj = generate_your_obj_somehow();
	setCache($cache_key, $obj, 60*60);
}

So, the idea is to use our cache if it exists. If not, generate our object and then store it in memcache. The above 60*60 will store the $obj for an hour.

Simple idea, but great performance! You can also set up background scripts to keep refreshing your frequently-used objects, so that there is no load time penalty for your users.

Bonus: install this script to see your memcache status! http://livebookmark.net/journal/2008/05/21/memcachephp-stats-like-apcphp/

ref: http://pureform.wordpress.com/2008/05/21/using-memcache-with-mysql-and-php/