Mdst3705 2013-01-24-php2

PHP 2

Prof AlvaradoMDST 3705

24 January 2013

Business• Reference materials posted• Use the principle of “TMI filtering”

– Filter out what has not been covered– Be comfortable with knowing a little

Review• Programming languages were invented so

that people could more easily control computers– Human like to interact with objects in the

world through language• But like natural languages, programming

languages involve worlds– Worlds are implied by code – Worlds are modeled in code– Worlds are created by code

We live in “Barricell’s Universe”

A world that has emerged from the use of a a specific kind of

computer

PHP as a language• Variables

– Variables are like nouns– Refer to locations in memory (pigeon holes)

• Values– Values are like meanings– Strings and numbers that are stored in

memory• Expressions

– Expressions, e.g. $x + 1, are like clauses– Expressions always “return” a value

Sentences• Code is written in sentences called

“instructions” Imperative and inquisitive modes– Imperative

• $x = $y; // Like saying, “Let $x = $y”• $x = 1 * 50 + $z;

– Inquisitive• If ($x == 1) {} // Like asking, “Is $x equal to 1?”

Sigils• $ as a prefix to variables

– Common in languages – Perl, Java, JavaScript

– Useful mnemonic device – avoids “Hungarian notation”

• Derives from medieval and renaissance magic– Sigil as a seal representing an angel or

demon – a “logo”• Also used as a personal logo

Todays Exercises• Emulate the 10 PRINT program in PHP• Learn about arrays, control structures,

and functions • Riff on the model to produce other

outcomes

Resources• PHP

– Manual from PHP’s Home Page– PHP for Absolute Beginners

• HTML and CSS– W3Schools