PHP Intro/Overview Squirrel Book pages 33-87

Server-side Scripting Everything you need to know in one slide 1.Web server (with PHP “plug-in”) gets a URL request: 2.Web server see’s that the page is.php 3.PHP Pre-processor searches the page for PHP code and executes the code. 4.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

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 servers 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’]}.”;

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

Constants define(“PI”, ); print PI; // outputs 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”; }

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

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 = ; $var = 39. “ Steps”; $var = 39 + “ Steps”;

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

Functions // Function definition function fname ($parameter1, $parameter2) { 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”;