Understanding PHP Basics: A Comprehensive Guide to Server-Side Scripting

PHP Intro/Overview Bird Book pages 1-11, 39-106

Server-side Scripting Everything you need to know in one slide • Web server (with PHP “plug-in”) gets a URLhttp://www.site.com/page.php • Web server see’s that the page is .php • PHP Pre-processor searches the page for PHP code and executes the code. • Web server sends back the output of the PHP code, not the code itself.

PHP Basics • PHP code can go anywhere in an HTML document as long as its in a PHP tag • Example <h1><?php echo “Hello World”; ?></h1>

PHP Variables • Variables do NOT have strict typing • Unless math operations are used, variables are strings by default • Variables must start with $ <?php $x = “Hello World”; echo $x; ?>

Commenting • 3 Types // Comment # Comment /* Comment Comment */

Print and Echo • Print can print strings print “42”; • Echo is more robust than print, it can print numbers and more than one parameter, separated by commas echo 42; // This will actually print 42 $x = “is” echo “The answer ”, $x, “ ”, 42;

Single Quotes vs. Double • These are the same… print “This works.”; print ‘This works also.’; • This makes it easy to print quotes print “Here is a ‘single quote’ ”; print ‘Here is a “double quote” ’;

New lines • The string variable $var contains a new line character  “Hello there\n sir!” $var = “Hello there sir!”; • Introducing new lines breaks makes it easer to write SQL queries that work…

SQL Example $query = “ SELECT max(orderid) FROM orders WHERE custid = $ID”; • If you send this query string to some database server it is important that the new line characters are in the string.

Variables in strings $x = 256 // “My computer has 256 MB ram.” $message = “My computer has $x MB ram.”; // “My computer has.” $message = “My computer has $xMB ram.”; Why?

Variables in strings $x = 256 // “My computer has.” $message = “My computer has $xMB ram.”; // “My computer has 256MB ram.” $message = “My computer has {$x}MB ram.”;

Variables in strings Using { } is very important when trying to include complex variables into other strings. $message = “Mars has a diameter of {$planets[‘Mars’][‘dia’]}.”;

Integers $var1 = 10; Floats $var2 = 6.1; Boolean $var3 = true; String $var4 = “true”; $var5 = ‘true’; $var6 = ‘10’; $var7 = “6.1”; Variables

Constants define(“PI”, 3.14159); print PI; // outputs 3.14159 Notice that constants don’t have $ Convention: Use all CAPS for constants BTW, PHP is case sensitive

Expression and Operators • Same as most high-level languages $z = 3; $x = 1; $y = 5.3; $z = $x + $y; $z++; $x += $y + 10; $z = $x * 10;

String concatenation • Not the same as JavaScript! $var1 = “Hello”; $var2 = “ world”; $var3 = $var1 + $var2; //This won’t work $var3 = $var1 . $var2;

Conditionals (if statements) • Same as other high-level languages if ($var < 5) { print “The variable is less than 5”; }

Compound conditionals if ($x == 1) { print “x is 1”; } elseif ($x == 2) { //  Notice elseif is one word print “x is 2”; } else { print “x is not 1 and not 2”; }

While $c = 0; while ($c < 10) { print $c . “ ”; $c++; } For for ($c = 0; $c < 10; $c++) { print $c . “ ”; } Loops

Loops: break for ($c = 0; $c < 10; $c++) { print $c . “ ”; if ($c == 5) break; }

Type Conversion $year = 2003; // This is an integer $yearString = strval($year); // $yearString is “2003” not an integer

Type Conversion • string strval(any other datatype) • integer intval(any other datatype) • float floatval(any other datatype)

Implicit type conversion • $var = “100” + 15; • $var = 100 + 15.0; • $var = 39 . “ Steps”; • $var = 39 + “ Steps”;

Implicit type conversion • $var = “100” + 15; // $var becomes int • $var = 100 + 15.0; // $var becomes float • $var = 39 . “ Steps”; // $var becomes string • $var = 39 + “ Steps”; // $var become int

Functions // Function definition function fname ($parameter1, $parameter2) { code; code; … return $returnvalue; } // Function call $x = fname(1,2);

Variable Scope (visibility) • Same as Java • Same as C++ function fun($x) { $temp = $x + 1; } fun(5); print “temp is: $temp”;

Understanding PHP Basics: A Comprehensive Guide to Server-Side Scripting