How do you build a singleton class in PHP? Can you?

[Phil Powell]

Consider this:

[PHP]
class ActionHandler {

/*-------------------------------------------------------------------------------------------------------------------------------------------------------------------
This class will be a singleton class structure by calling its
constructor by reference only (prefixed by '&'). Is primarly used to
reference its errorArray Array property as a single reference to
allow for static usage
--------------------------------------------------------------------------------------------------------------------------------------------------------------------*/

var $isSuccessful = true; // BOOLEAN PROPERTY DETERMINING IF
ACTION WAS SUCCESSFUL
var $tableName; // DB TABLE NAME PROPERTY
var $fileName; // FILE NAME PROPERTY
var $dbConn; // DB CONNECTION OBJECT
var $dbConnObj; // DB RESOURCE LINK OBJECT
/*---------------------------------------------------------------------------------------------------------------------------------------------------------
Remember that you since this class will be extended by other classes
especially in action.inc.php, for properties to
have value into the class this extends into, you will have to not
"construct" them here since this constructor will not
be called directly by the extended class.
------------------------------------------------------------------------------------------------------------------------------------------------------------*/
function &ActionHandler() { // SINGLETON CONSTRUCTOR
static $errorArray = array(); // ASSOCIATIVE ARRAY PROPERTY
FIELD => ERROR MSG
}

//----------------------------------------------------* GETTER/SETTER
METHODS *--------------------------------------------------------------

function &getErrorArray() { // STATIC ARRAY METHOD
return $this->errorArray;
}
function &getHTMLRedirect($myImmedAction, $additionalQS = '') { //
STATIC HTML/JAVASCRIPT STRING METHOD
global $section, $clientFolderName, $projectFolderName,
$redirectArray;
if ($redirectArray[$section][$myImmedAction] && $myImmedAction) {
$html = "\n<script>\n <!--\n location.href =
'/$clientFolderName/$projectFolderName/index.php?section=$section&action="
..
$redirectArray[$section][$myImmedAction] .
'&success=' . urlencode($this->getSuccessMsg());
$html .= ($additionalQS) ? '&amp;' . urlencode($additionalQS) : '';
$html .= "';\n //-->\n</script>\n<noscript>\n<meta
http-equiv=\"Refresh\"
content=\"1;URL=/$clientFolderName/$projectFolderNameindex.php?" .
"section=$section&action=" .
$redirectArray[$section][$myImmedAction] . '&success=' .
urlencode($this->getSuccessMsg());
$html .= ($additionalQS) ? '&amp;' . urlencode($additionalQS) : '';
$html .= "\">\n</noscript>\n\n";
}
return $html;
}

function &getSuccessMsg() { // STATIC STRING METHOD
global $action, $choice, $db;
return 'Successful ' . strtoupper($action) . ' ' .
strtoupper($choice) . " to database $db - <a
href=index.php?willViewLog=1>View Log</a><p>";
}

function setErrorArray($additionalErrorArray) { // VOID METHOD
if (is_array($this->errorArray) && @sizeof($this->errorArray) > 0 &&
is_array($additionalErrorArray) && @sizeof($additionalErrorArray) > 0)
{
$this->errorArray =& $this->errorArray + $additionalErrorArray;
} elseif (is_array($additionalErrorArray) &&
@sizeof($additionalErrorArray) > 0) {
$this->errorArray =& $additionalErrorArray;
}
}

//--------------------------------------------------* END OF
GETTER/SETTER METHODS
*-------------------------------------------------------------------------

function &convert_to_HTML($content) { // STATIC HTML STRING
METHOD
$content = preg_replace('/[\n\r]/i', '<BR>', $content);
$content = preg_replace('/[\s]/i', '&nbsp;', $content);
return $content;
}

function &convert_to_text($content) { // STATIC TEXT STRING
METHOD
$content = preg_replace('/<br[^>]*>/i', '\n', $content);
$content = preg_replace('/&nbsp;/i', '\s', $content);
return $content;
}

}
[/PHP]

THAT is my entire supposed Singleton class in its actual entirety. It
is set up that way to call static methods upon a static array. That
way, whenever you have this call in your class:

[PHP]
if (somethingsWrong) ActionHandler::setErrorArray('action' =>
'Something is wrong'));
[/PHP]

However, consider this example: I call an instance of a FileGenerator
class from my ActionPerformer->perform() method. FileGenerator class
object's getBackupFile() method does some code and if it breaks:

[PHP]ActionHandler::setErrorArray('action' => 'Something is
wrong'));[/PHP]

Everything in the FileGenerator class object method works just fine
and were I to do this:

[PHP]print_r(ActionHandler::getErrorArray());[/PHP] I see:

Array (action => Something is wrong)

But the moment I leave the getBackupFile() method from FileGenerator
class object and return to the code in ActionPerformer->perform()
method and were I do this:

[PHP]print_r(ActionHandler::getErrorArray());[/PHP] I see:

Array ()

How then in PHP do you assure that anytime I call
ActionHandler::setErrorArray() that the error array, which is supposed
to be static, remains a single-instance entity with a value available
to ALL classes everywhere? How do you build a singleton class in PHP?

Phil

[Phil Roberts]

With total disregard for any kind of safety measures
so*****@erols.com (Phil Powell) leapt forth and uttered:

How do you build a singleton class in PHP?

class Singleton {
function &instance() {
static $instance = false;
if(!$instance) {
$instance = new Singleton;
}
return $instance;
}
}

$obj =& Singleton::instance();

--
Phil Roberts | Nobody In Particular | http://www.flatnet.net/