2.3. Zend_Cache frontends

2.3.1. Zend_Cache_Core

2.3.1.1. Introductie

Zend_Cache_Core is een speciale frontend omdat het de kern van de module is. Het is een generieke cache frontend en wordt uitgebreid door andere classes.

[Opmerking] Opmerking

Alle frontends erven van Zend_Cache_Core zodat zijn methodes en opties (zoals hieronder beschreven) ook beschikbaar zijn in andere frontends, dus ze zullen hier niet worden gedocumenteerd.

2.3.1.2. Beschikbare opties

Deze opties worden doorgegeven aan de factory methode zoals hierboven gedemonstreerd.

Tabel 2.1. Beschikbare opties

Optie Data Type Standaard Waarde Omschrijving
caching boolean true zet de caching aan of uit (kan handig zijn om te debuggen)
lifeTime int 3600 Levensduur van de cache (in seconden), wanneer de waarde null is, blijft de cache altijd geldig.
logging boolean false Wanneer dit op true staat, wordt logging via Zend_Log aangezet (maar wordt het systeem trager)
writeControl boolean true Zet schrijfcontrole aan (de cache wordt direct na schrijven gelezen om corrupte records te herkennen), door writeControl aan te zetten zal de cache iets trager wegschrijven maar het lezen wordt niet trager (het kan sommige corrupte cache bestanden herkennen maar is geen perfecte controle)
automaticSerialization boolean false Zet de automatische serialisatie aan of uit, dit kan worden gebruikt om direct informatie op te slaan dat geen string is (maar het is trager)
automaticCleaningFactor int 0 Stel het automatische opschoonsysteem in (garbage collector): 0 betekent geen automatische opschoning, 1 betekent systematisch cache opschonen en x > 1 betekent willekeurig opschonen 1 keer per x schrijf operaties.

2.3.1.3. Voorbeelden

Een voorbeeld wordt gegeven aan het begin van de handleiding.

Wanneer je alleen strings in de cache wil opslaan (want met "automaticSerialization" is het mogelijk ook sommige booleans op te slaan), kan je een compactere constructie gebruiken:

<?php  
             
// we gaan er vanuit dat je $cache al hebt

$id = 'mijnGroteLoop'; // cache id van "wat we willen cachen"

if (!($data = $cache->get($id))) {
    // cache miss
    
    $data = '';
    for ($i = 0; $i < 10000; $i++) {
        $data = $data . $i;
    }
    
    $cache->save($data);
    
} 

// [...] doe iets met $data (echo het, stuur het door enz.)
             
?>       

Als je meerdere blokken of data instanties wilt cachen, is het idee hetzelfde:

<?php  
             
// Zorg ervoor dat je unieke identifiers hebt:
$id1 = 'foo';
$id2 = 'bar';

// blok 1
if (!($data = $cache->get($id1))) {
    // cache miss
    
    $data = '';
    for ($i=0;$i<10000;$i++) {
        $data = $data . $i;
    }
    
    $cache->save($data);
    
} 
echo($data);

// Dit wordt niet door de cache beinvloed
echo('NOOIT GECACHED! ');

// blok 2
if (!($data = $cache->get($id2))) {
    // cache miss
    
    $data = '';
    for ($i=0;$i<10000;$i++) {
        $data = $data . '!';
    }
    
    $cache->save($data);
    
} 
echo($data);

?>       

2.3.2. Zend_Cache_Frontend_Output

2.3.2.1. Introduction

Zend_Cache_Frontend_Output is an output-capturing frontend. It utilizes output buffering in PHP to capture everything between its start() and end() methods.

2.3.2.2. Available options

This frontend doesn't have any specific options other than those of Zend_Cache_Core.

2.3.2.3. Examples

An example is given in the manual at the very beginning. Here it is with minor changes:

<?php

// if it is a cache miss, output buffering is triggered
if(!$cache->start('mypage')):

// output everything as usual
echo 'Hello world! ';
echo 'This is cached ('.time().') ';

$cache->end(); // output buffering ends
endif;

echo 'This is never cached ('.time().').';

?>       

Using this form it is fairly easy to set up output caching in your already working project with little or no code refactoring.

2.3.3. Zend_Cache_Frontend_Function

2.3.3.1. Introduction

Zend_Cache_Frontend_Function caches the results of function calls. It has a single main method named call() which takes a function name and parameters for the call in an array.

2.3.3.2. Available options

Tabel 2.2. Available options

Option Data Type Default Value Description
cacheByDefault boolean true if true, function calls will be cached by default
cachedFunctions array   function names which will always be cached
nonCachedFunctions array   function names which must never be cached

2.3.3.3. Examples

Using the call() function is the same as using call_user_func_array() in PHP:

<?php

$cache->call('veryExpensiveFunc', $params);

# $params is an array
# for example to call (with caching) veryExpensiveFunc(1, 'foo', 'bar'), you will use
# $cache->call('veryExpensiveFunc', array(1, 'foo', 'bar'))

?>       

Zend_Cache_Frontend_Function is smart enough to cache both the return value of the function and its internal output.

[Opmerking] Opmerking

You can pass any builtin or user defined function with the exception of array(), echo(), empty(), eval(), exit(), isset(), list(), print() and unset().

2.3.4. Zend_Cache_Frontend_Class

2.3.4.1. Introduction

Zend_Cache_Frontend_Class is different from Zend_Cache_Frontend_Function because it allows caching of object and static method calls.

2.3.4.2. Available options

Tabel 2.3. Available options

Option Data Type Default Value Description
cachedEntity (required) mixed   if set to a class name, we will cache an abstract class and will use only static calls; if set to an object, we will cache this object methods
cacheByDefault boolean true if true, calls will be cached by default
cachedMethods array   method names which will always be cached
nonCachedMethods array   method names which must never be cached

2.3.4.3. Examples

For example, to cache static calls :

<?php

class test {
   
    # Static method
    public static function foobar($param1, $param2) {
        echo "foobar_output($param1, $param2)";
        return "foobar_return($param1, $param2)";   
    }

}

// [...]
$frontendOptions = array(
    'cachedEntity' => 'test' // The name of the class
);
// [...]

# The cached call
$res = $cache->foobar('1', '2');

?>       

To cache classic method calls :

<?php

class test {
   
    private $_string = 'hello !';
      
    public function foobar2($param1, $param2) {
        echo($this->_string);
        echo "foobar2_output($param1, $param2)";
        return "foobar2_return($param1, $param2)";   
    }

}

// [...]
$frontendOptions = array(
    'cachedEntity' => new test() // An instance of the class
);
// [...]

# The cached call
$res = $cache->foobar2('1', '2');

?>       

2.3.5. Zend_Cache_Frontend_File

2.3.5.1. Introduction

Zend_Cache_Frontend_File is a frontend driven by the modification time of a "master file". It's really interesting for examples in configuration or templates issues.

For instance, you have an XML configuration file which is parsed by a function which returns a "config object" (like with Zend_Config). With Zend_Cache_Frontend_File, you can store the "config object" into cache (to avoid the parsing of the XML config file at each time) but with a sort of strong dependency on the "master file". So, if the XML config file is modified, the cache is immediatly invalidated.

2.3.5.2. Available options

Tabel 2.4. Available options

Option Data Type Default Value Description
masterFile (mandatory) string the complete path and name of the master file

2.3.5.3. Examples

Use of this frontend is the same than of Zend_Cache_Core. There is no need of a specific example - the only thing to do is to define the masterFile when using the factory.

2.3.6. Zend_Cache_Frontend_Page

2.3.6.1. Introduction

Zend_Cache_Frontend_Page is like Zend_Cache_Frontend_Output but designed for a complete page. It's impossible to use Zend_Cache_Frontend_Page for caching only a single block.

On the other hand, the "cache id" is calculated automatically with $_SERVER['REQUEST_URI'] and (depending on options) $_GET, $_POST, $_SESSION, $_COOKIE, $_FILES. More over, you have only one method to call (start()) because the end() call is fully automatic when the page is ended.

For the moment, it's not implemented but we plan to add a HTTP conditional system to save bandwith (the system will send a HTTP 304 Not Modified if the cache is hit and if the browser has already the good version).

[Opmerking] Opmerking

Zend_Cache_Frontend_Page is really "alpha stuff" and is meant to be improved further down the road.

2.3.6.2. Available options (for this frontend in Zend_Cache factory)

Tabel 2.5. Available options

Option Data Type Default Value Description
httpConditional boolean false use the httpConditional system (not implemented for the moment)
cacheWith{Get,Post,Session,Files,Cookie}Variables boolean false if true, cache is still on even if there are some variables in the corresponding superglobal array ; if false, cache is off if there are some variables in the corresponding superglobal array
makeIdWith{Get,Post,Session,Files,Cookie}Variables boolean true if true, we have to use the content of the corresponding superglobal array to make a cache id if false, the cache id won't be dependent of the content of the corresponding superglobal array

2.3.6.3. Examples

Use of Zend_Cache_Frontend_Page is really trivial :

<?php
	           
// [...] // require, configuration and factory
	
$cache->start();
# if the cache is hit, the result is sent to the browser and the script stop here
	
// rest of the page ...
	
?>