Workshop in Computational Bioskills

Workshop in Computational Bioskills - Lesson 11


Workshop in Computational Bioskills - Spring 2006

Lesson 9 - PHP Basics

Introduction
Variables
Arrays
Control Flow

PHP - Dynamic Web Pages Language PHP - programing language, used for writing dynamic web pages, when the page content depends on the user input.

Several facts on PHP

Embedded within HTML language

The PHP code is being executed by the web server (e.g. Apache) When the client asks for a .php page Apache calls the PHP interpreter, and the last one executes the script in the page and returns the result page.

PHP vs. JavaScript: PHP is a server-side language, and JavaScript is a client-side language, i.e. the client is the one who executes the code.

Lessons were prepared following Learning PHP 5 by David Sklar (O'Reilly).

A useful site for learning both HTML and PHP is www.w3schools.com

Another one (in hebrew): http://php.eitan.ac.il/main.php

Another one (in hebrew): www.webmaster.org.il

Why PHP?

Simple language

Custom-made - PHP was generated for the purpose of writing websites. For instance - common actions in websites has a convenient interface.

Cross platform

Free, and with open source

PHP vs. CGI-Bin: PHP us much more friendly (learned from the experience in last years).

Getting Started
File Hello_world.php: <html> <head> <title> PHP Hello </title> </head> <body> <b> <? print "Hello World!" ?> </b> </body> </html>

A PHP file has ".php" suffix.

It lives within HTML code, in special tags <? ?>. The PHP interpreter looks only on the text within the tags.

The key words are all case-insensitive.

Comments like in C++ : // or /* */

Run Hello_world.php

But that was not really dynamic (why?). Let's see for example how to create a simple_form.php. If you want, recall how to write form in Lesson 7.

Strings
PHP has two data types: strings and numbers.
Strings appear in three formats: Single quotes: <? print 'That\'s your name: $name' ?> // That's your name: $name Double quotes: <? print "Your name is $name" ?> // Your name is Dubi Here-document (Heredoc) syntax: <? print <<< HTMLBLOCK <html> <body> some text... </body> <html> HTMLBLOCK ?> Prints all the text between the HTMLBLOCK tags
Useful string functions

trim( $string ) removes whitespace from the beginning and end of a string.

strlen( $str ) returns the length of the string.

printf( format, $str ) formated print, like in C and Perl.

strcasecmp( $str1, $str2 ) compares the strings, case insensitive.

strtolower( $str ) and strtoupper( $str ) - change the string to be all lower case or upper case. ucwords( $str ) upper case the first letter of each word in the string

substr($str, offset, length) extract length number of chars from the string, starting in offset. If offset is negative, it is defined from the end.

str_replace( $substr, $rep, $string ) replace each appearance of $substr with $rep

Let's see a simple example for manipulating text

Numbers
No much to say here - just like in perl and other languages.

Boolean
false is represented by the empty string, empty array and the number zero.

Variables
o Like the perl scalars. o Naming convention - letters, underscore and numbers (not in the beginning). o Arithmetic operations permitted: just like perl. o Variables inside strings: $preparation= 'Braise'; $meat = 'Beef'; print "{$preparation}d $meat with Vegetables"; // Braised Beef with Vegetables