OK, Plug it in Now - PHP

If you read the first article in this series, you’d know that we’re about to start talking about the plug-in and module system for our site engine. Along with the plug-ins and modules, we’re also going to be discussing some of the general functions that are needed to make site engine work correctly.

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By: James Murray

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June 14, 2004

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Now that the past couple of classes are all set up, we're ready to start loading up all our plug-ins. Well, we're ready to make the class that will load them. First we'll select the plug-in ID, name, directory, and file from the database. Then we'll set them all to an array in the plug-ins class, that way the information about the plug-ins can be used later without having to select it from the database again. After we've built our list of initialized plug-ins, we'll use a function that will actually load the plug-ins and include them into our engine. With that all said, let's take a look at the class file.

<?PHP
class plugins{
    public $pcount;    //this will hold the number of plug-ins that we actually load into the engine
    public $plugin_list;    //this will hold our array of plug-in information
    public $plugin_error;    //this will hold any errors that are produced by loading a plug-in
    public $lcount;    //this will hold the number of plugins in our plug-ins list

    function plugins($site_id=""){    //we name the main function the same as the class so that it initializes when the class is called
        global $sql,$site;    //this requests the $sql and $site classes as a global variables
        $this->pcount=0;    //set the default of $pcount to 0 because we don't yet have any plug-ins loaded
        $this->lcount=0;    //set the default of $lcount to 0 because we don't yet have any plug-ins in the plug-ins list
        if($site_id==""){    //check to see if the administrator overrides the $site_id to list plug-ins for other sites
            $site_id = $site->site['ID'];    //if the site_id isn't overridden set it to the current site's id
        }
        $plugins_list=$sql->_query("SELECT
                                         plugins.plugin_ID,
                                         plugins.plugin_name,
                                         plugins.plugin_dir,
                                         plugins.plugin_file
                                     FROM
                                         plugin_status,
                                         plugins
                                     WHERE
                                         plugins.plugin_ID = plugin_status.plugin_ID AND
                                         plugin_status.site_ID = '$site_id' AND
                                         plugin_status.plugin_status = 'initialized'
                                     ORDER BY
                                         plugins.plugin_priority DESC");    //select all the initialized plug-in information from the database
        while($plugin=$sql->_fetch_object($plugins_list)){    //start a loop to get the information from the select query using the _fetch_object function
            $this->lcount++;    // update lcount for each plug-in we add to the plug-ins list
            $this->plugin_list['plug_ID'][]=$plugin->plugin_ID;    //add the current plug-in's ID to the plugin list
            $this->plugin_list['plug_name'][]=$plugin->plugin_name;    //add the current plug-in's name to the plugin list
            $this->plugin_list['plug_dir'][]=$plugin->plugin_dir;    //add the current plug-in's directory to the plugin list
            $this->plugin_list['plug_file'][]=$plugin->plugin_file;    //add the current plug-in's file to the plugin list
        }
        if($this->pcount==0){    //check to see if any plug-ins have been loaded into the engine
            $this->load();    //if no plug-ins are loaded, call the load() function to load the plug-ins
        }
    }

    function load(){    //this function loads the plug-ins from the plug-ins list
        if(is_array($this->plugin_list)){    //make sure that the plug-ins list as an array, to prevent errors
            for($i=0;$i<$this->lcount;$i++){    //start a loop to identify each plug-in in the plug-ins list
                if(file_exists("{$this->plugin_list['plug_dir'][$i]}/{$this->plugin_list['plug_file'][$i]}/main.plug.php")){    //make sure the plug-in's file exists, to prevent errors
                    @include("{$this->plugin_list['plug_dir'][$i]}/{$this->plugin_list['plug_file'][$i]}/main.plug.php");    //include the plug-in into the engine
                    $this->pcount++;    //update pcount for each plug-in that loads
                }else{
                    $this->plugin_error[]="The plug-in file: <b>/{$this->plugin_list['plug_dir'][$i]}/{$this->plugin_list['plug_file'][$i]}/main.plug.php</b> Does not exist";    //if the plug-in cant load add an error to the error list
                }
            }
        }
    }
}
?>