Outline

• Getting Help within Yioop
• Media Updater
• Feed Update Job
• Other Things Yioop Can Do
• In-Class Exercise
• PHP

Introduction

• Last week, we looked at the Yioop search engine which is coded in PHP.
• We will finish up our first quick overview of Yioop in a moment.
• This semester we will make use of the Yioop search engine as an information retrieval library from time to time in this class.
• In order to understand how to do this, we also need to know how to write a little PHP.
• So today, we are also going to give a brief tutorial on how to do this.

Getting Help Within The App

• Yioop comes with an integrated wiki-based help system.
• Next to various widgets in the interface there is a question mark icon:
• Clicking on such an icon will bring up help about the adjacent widget. This might look like:
• Notice the help box has an edit link. This can be used to go to Yioop's wiki system and edit the help box if it needs to be improved.

Media Updater

• So far we've seen that Yioop has the main processes:
  1. Name Server - This is essentially the same as the Web App below if Yioop is running on at a single url (usually a different urls corresponds to different machines). If Yioop is run on multiple urls, one url will be configured to be a Name Server, and it is used for global messaging of information like the current crawls.
  2. Web App - this runs under a web server and is used to display search results, as well as user groups and wiki's. It also is used for sending messages between other processes.
  3. Queue Server - this consists of two sub-processes: (a) an indexer used to compute an inverted index from downloaded/imported documents, (b) a priority queue which handles what documents to process next.
  4. Fetcher - get fetch batches from queue servers and then does initial downloading and processing of document before sending the result back to the appropriate queue server.
• In addition to crawling, there are many ongoing tasks that a web site might need to do for maintainence: compute usage analytics, bulk emailing, updating news and podcast feeds as well as trending information, compute group and feed item recommendations for users, convert uploaded media content to common media formats (convert to mp4, strip exif from images, etc).
• Yioop handles these tasks in with its Media Updater process which can be managed under Machines:
  
• The MediaUpdater only runs when it is turned on.

Controlling Jobs of the Media Updater

• Clicking the [Configure Media Jobs] link on the Manage Machines page takes one to a page:
  
• As can be seen by the [Name Server|Distributed] toggle, MediaUpdater jobs can be configure to run either only on the name server or across all machines in a Yioop site.
• The list beneath this shows a list of found media jobs for the MediaUpdater, and whether the job is active (On) or not (Off).
• To determine the Job list, Yioop looks in the folders: src/library/media_jobs (built-in) and work_directory/app/library/media_jobs (you can add new jobs here) for files with the suffix Jobs.php.
• We now focus on the FeedsUpdate Job which is responsible for downloading news feed items periodically for news searches.

Search Sources

• The Search Sources Activity can be used to add, edit, test, and delete feed search sources that the FeedsUpdate Job downloads each hour to look for feed items.
  
• Clicking the "+" button next to Media Sources lets you fill in a form to add a new source:
• The Media Kind drop down lets you choose which of several common news feed formats the to-be-downloaded-periodically url is. These include RSS/ATOM, JSON, scraped using XPaths from and HTML document, scraped using regex formats.
• The default Yioop install comes with several example feeds.
• The feeds currently added can be tested for their behavior using their Test links.

Other Things Yioop Can Do

• Recall under the Server Settings activity one can configure whether or not and how Yioop will supports the registration of users in addition to the default root account.
• Under the hamburger menu, Social activities group:
  
  are four activities used in managing and viewing groups of discussions and wikis within Yioop.
• On the account landing page one also has the following group of button icons:
  
  
• The first link/icon takes one to the direct messaging activity to allow one to direct directly communicate between a pair of users.
• The next link/icon takes one to a combined discussions view of all the discussions going on in groups a user is subscribed to.
• The My Groups/houses icons shows a list of groups a user currently belongs to. Each group comes with its own discussion Feed and Wiki, and from this page one can directly access these.
• The Join Groups/landing icon lets you search for and join existing groups, and the "+" icon lets you create new groups.
• On install, Yioop comes with three built in groups: Help, Public, and Search. Each user also gets a private group whose feed is used to handle direct messaging and whose wiki is used to maintain the users between group clipboard.
• The three built-in groups are configured by default to be only editable by the admin account.
• The Help group has the wiki pages for the built-in help system for Yioop.
• The Public wiki together with the Appearance activity in Yioop can be used to control the look of a Yioop web site. For example, the seekquarry.com website is a vanilla install of Yioop where this has been done to change its appearance.
• The Search Group is used to stored edited search results as well as wiki-callout search results. These can be configured under the Results Editor.
• The Configure activity is another useful activity. You can use it to turn on Query info and Error Info. These can be used to understand what iterators Yioop will use in processing a query.

Introduction to PHP

• PHP was developed by Rasmus Lerdorf around 1994-1995.
• PHP originally stood for Personal Home Page, later PHP became an acronym for PHP: Hypertext Processor.
• It is one of the most common server-side programming languages.
• The Wikipedia article on PHP says as of Jan 2023, 77.8% of all the websites whose server-side programming language is known use PHP.
• One oft-touted advantage of PHP is its shared nothing architecture: Each php request is distinct and does not directly share memory/data with other requests. Shared data is stored in filesystem/memory cache/database/etc.
• This can make PHP easier to debug and easier to scale.

Getting and Running PHP

• The web site for PHP is https://www.php.net/
• PHP can either be run from the command-line, run through a web server module, or fast-cgi.
• When run from a web server, the server determines that a page is PHP usually by looking for one of the extensions .php, .php3, .phtml
• When executing a PHP page, the PHP processor takes a PHP document and starts processing in one of two modes.
• By default, it simply copies it to the output. (Copy mode).
• When it sees a start PHP indicator (using <?php or <?=) it executes code and writes the result to the output until it sees a stop PHP indicator (?>)(Interpretive mode).
• A stop PHP indicator switches processing back into copy mode.
• PHP is typically interpreted but it also can be precompiled.
• The syntax of PHP is closely related to Perl, Javascript, and Java.

Example PHP file

Consider the file test.php:

hello world
<?php
echo "hello world";
?>
yeah!!
<?php
echo "okay";

If we ran this from the command line using:

php test.php

This would output:

hello world
hello worldyeah!!
okay

More On PHP

• PHP proceeds top-down when going through a file. Single statements in global scope are just executed.
• In global scope, we can also define new functions and classes.
• These can then be used in later global scope statements.
• For example,

  <?php
  function foo()
  {
     echo "hi";
  }
  foo(); // prints hi
  

• PHP can use either Perl, C++, or C comments: #, //, /* ... */

In-Class Exercise

• Install PHP.
• Make a file test.php which outputs "Hello," using copy mode, then calls a function mrPresident() (after defining it).
• Implement the function mrPresident() so that it echo's your actual name.
• Please post your solutions to the Sep 6 In-Class Exercise Thread.

Configuring PHP

• You can fine-tune how PHP runs by editing the file php.ini
• A ';' is used to indicate a comment in this file.
• One common thing to change is the amount of error reporting PHP gives.
• By default, it is assumed we are in a production environment so none is given.
• For today, we want error-reporting. So find the line:

  ;error_reporting = E_ALL & ~E_NOTICE
  

  and uncomment it, restart Apache

PHP configuration

You can see what PHP's configuration settings are in use by the following small program

<?php
phpinfo();

Primitives and Variables

• PHP has four scalar types: boolean, integer, double, and string.
• There are also two compound types: array and object and two special types: resource and null.
• PHP is dynamically typed: you don't need to specify the types of variables before using them.
• Variable names are alphanumeric+underscore strings beginning with a dollar sign: $my_var, $fooFOO1999, etc. The first character after the $ is not allowed to be numeric.
• Yioop coding guidelines are to use variables with meaningful names where words are separated by underscores.
• PHP does variable assignments like most languages:

  $a = 53;
  $b = $a + 1;
  

• An unassigned variable is sometimes called an unbound variable and has value null. This can be coerced to one of the other types depending on the context.
• To check if a variable is currently bound you can use the isset($variable_name) function. This returns true or false (one of the two Boolean values, case-insensitive).
• empty($variable_name) can be used for isset($variable_name) && $variable_name != null.
• You can also call error_reporting(-1), to set PHP's error reporting level to report all errors, warnings, notices, etc. so that it prints unbound variables.
• PHP also has useful functions for printing out the values of variables: var_dump, print_r.