Outline

• Finish CSS - Text-alignment, Box Model, Positioning Elements
• Keyboard Shortcuts
• Quiz
• Overview of PHP
• Datatypes
• Control Statements
• Arrays

Alignment of Text

• Last week, we were discussing Cascading Stylesheets - a means to control how the various elements on a web page are displayed.
• We were going over the slide below on text aligning and positioning...
• There are several properties which control the flow of text and images in a given set of tags.

  text-indent

  Usually used to control how much the first line of a paragraph is indented. Ex: p.indent {text-indent: 0.5in}

  text-align

  This controls how the text is aligned within margins. It can have the values: left, right, center, and justify.

  float

  This property often used with images and tables to control how text flows around the element. possible values are left, right, and none. The float tag can be used to make a simple two column layout (float one div tag to the left and set its width, follow it by another div tag). Recall that HTML 5 introduced several new semantic containers tags such as: header, footer, main, nav, section -- float is a very useful tool in doing the layout for these tags.

Box Model

• Each element in XHTML/HTML has properties which control its border and the amount of white space around it.
• This is called the box model:
  
• This model is also used when you use CSS with other kinds of XML documents.

More on the Box Model

• We next look at properties to control the box model. In addition to thhe ones below, thhere are also the master properties border:, padding:, margin: which can take a white space separated list of properties from thhe below.
• Controlling the border:

  border-style:

  This can be none, solid, dotted, dashed, double

  border-width:

  This can be a length in pixels or thin, medium, or thick. You can more finely control each side of the border by using the properties: border-top-width, border-bottom-width, border-left-width, bottom-right-width.

  border-color:

  This sets the color of the border. This can also be more finely controlled with border-top-color, border-bottom-color, border-left-color, and border-right-color.

  border-radius:

  Sets the radius of a circle used to curve the corners of a box. Default is 0. You can give it a single value or list each of thhe four corners.

• Controlling margins and padding: These can be controlled using the properties: margin-left, margin-right, margin-top, margin-bottom, padding-left, padding-right, padding-top, padding-bottom.
• For block elements like the table tag, we use the margin property if we want to center them within a container -- you can't do this with text-align. To do this, set the left and right margin to have value auto and then define the table's width.

Background Images

• The background-image property is used to place an image in the background of an element:

  body {background-image: url(background.jpg);}
  

• The way this image is displayed can be further controlled using the properties:

  background-repeat:

  this may have values: no-repeat, repeat-x, repeat-y

  background-position:

  this may have values which are space separated combinations of top, center, bottom, left, and right. You can also give an x and y value for the image offset in each direction. This is useful for sprites.

Position and Display Properties

• The position property can have the value static (default), relative (says to place element relative to the last element), absolute (says to place element at some offset from top left of containing element), fixed (keep at that location even if scroll bar used).
• For example,

  <style type="text/css"> 
     p.first {position: absolute; top:1in; left:2in;}
     p.second {position: relative; left:-1in;}
  </style> 
  <p class="first">displays one inch down 
  two inches from left of top of screen</p>
  <p class="second">displays 1inch to the left 
  of where the first paragraph finished</p>
  

• The display property can take values block, inline, inline-block or none. block causes the box model to be used, inline makes the element data flow like text, and none does not render the element. You can also set the property "visibility: hidden" which renders the element in the background color
• Other useful properties are width and height which set and control respectively the width and height of an element.

Keyboard Shortcuts

• We are now done talking about CSS.
• As a brief interlude before beginning our next major topic -- which is PHP-- I thought I would point out a useful way to make web pages more accessible.
• This is to use the accesskey attribute of an element within the web page:

  <input type="text" name="fname" accesskey="f" />
  

• Now when ALT-f (maybe CTRL-ALT-f on a Mac) is typed the focus will go directly to this element.

Quiz

Which of the following statements is true?

1. The CSS border attribute cannot be used to control the width of the border of an element.
2. Only style attributes of one class selector are ever applied to an element.
3. The label tag is used to associate text with a control/widget element on a form.

Introducing 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.
• According to Tiobe, it is ranked eigth in overall popularity amongst all languages for any use.
• The Wikipedia article on PHP says over 20 million domains are hosted on servers with PHP enabled.
• Sites such as Yahoo, Facebook, Wikipedia, Slack, Dailymotion, Digg are written in a flavor of PHP. Yahoo is transitioning to Node.js. Wordpress, Drupal, Joomla, vBulletin, phpBB, Laravel, Symfony, MantisBT, Roundcube etc are written in PHP.
• Here is a list of what popular websites use.
• The most recent version of PHP is PHP 8.0. The big advantage of PHP 7.x over PHP 5.x is that its interpreter is almost twice as fast.
• PHP 8.x introduces a just in time (JIT) compiler, more language features, and better type checking in general, further speeding up the language.
• If you believe in language benchmarks... PHP tends to be faster than Python (more than twice as fast on all benchmarks where programs were parallelized equivalently).
• 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.
• I.e., if your program crashes, it doesn't tend to crash the whole server.
• This can make PHP easier to debug and easier to scale.

Overview

• There is more than one implementation of PHP. The most common is available at php.net.
• Facebook's hhvm is an alternative implementation to PHP that runs at speeds comparable to PHP 8. It also interprets the Hack language -- a typed variant of PHP. hhvm is used by Facebook and Wikipedia.
• A web server determines that a page is PHP usually by looking for one of the extensions .php, .php3, .phtml, etc
• When called from the web server on a PHP page, the PHP processor takes a PHP document and starts processing in one of two modes.
• When it sees XHTML it simply copies it to the output. (Copy mode).
• When it sees PHP code it executes the code and writes the result to the output.(Interpretive mode)
• PHP is typically interpreted but it also can be precompiled.
• The syntax of PHP is closely related to Perl and Javascript.

Configuring PHP

• PHP should be installed and running on your machines as of HW1.
• PHP can be run either using the Apache module, using fast-cgi, from the command line, or using the built-in web-server that comes with PHP (> 5.4.4).
• From the command line:
  

  php name_of_script.php #runs name_of_script.php
  php -a # run in enter interactive mode. will get a prompt...
  php > echo "hello world";
  hello world
  php > quit
  cd ~/public_html 
  php -S localhost:8000 #starts built-in web server on port 8000
      # using current dir as document root
  

• You can fine-tune how PHP runs by editing the file php.ini
• A ';' is used to indicate a comment in this file.
• The most common thing for people to change is to have a line:

  short_open_tag = On
  

  so that you can escape to a PHP script using <? rather than <?php
• Unfortunately, using the short open tag can mean your script is not as portable so for this class we will leave this off.
• Xampp sets things this way by default so for today we will not worry about this. -- Many open source projects prefer long tags for compatibility.
• Another 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