PHP

PHP Server-side Programming

PHP • PHP stands for PHP: Hypertext Preprocessor • Originally Personal Home Page • PHP is interpreted • PHP code is embedded into HTML code • interpreter is invoked by the web server • Syntax is similar to C, Java, Perl etc. • Think of a cross between perl and C • PHP is open source, free, available for most platforms, popular

What can you do with PHP • Generate content as an HTML page is loaded (generate HTML code) • User sees only the generated code, not your PHP code • Respond to a form with dynamic content • Retrieve and display information from a database or server-side files

Where does the PHP code go? • PHP code goes into a special element type in your HTML files. <?php … ?> • You can have multiple php elements in a page • Code in the php element is sent to the php interpreter; everything else is assumed to be content • File needs to have a .php or .phtml extension

HelloWorld in PHP <html> <head> <title>PHP</title> </head> <body> <?php echo 'Hello, world!' ?> </body> </html>

Basics • Syntax is similar to C and perl • Comments • // • /* */ • # • Statements are terminated by semicolon • { … } is compound statement, not a block • Whitespace insensitive • Reserved words, function names are case-insensitive

More Basics • Variable names (case-sensitive) same as for Java with a $ in front • can be assigned by value or by reference • Dynamically typed • For output use • echo • print • printf just like in C

Here Documents • Instead of using multiple print statements, use a here document print <<<_HTML_ <html><head> … </head> <body> … </body></html> _HTML_ • Everything between the two _HTML_ is printed

Primitive boolean integer float string Compound array (similar to hash in perl) object - defined by a class Special types NULL resource Built-In Types

Strings • Use either double or single quotes for strings • In single-quoted strings, all characters are interpreted literally • Variables and escape characters are interpreted in double-quoted strings • Strings can extend over multiple lines

String functions • trim removes leading and trailing whitespace • ltrim and chop remove from one end • strlen gives number of characters in the string • == can be used to compare strings (case sensitive) • strcasecmp() compares strings ignoring case (semantics of C strcmp) • Use . for concatenation • get substrings using substr( string, start, length)

Numbers • PHP distinguishes between integer and floating point values • Usual set of arithmetic operations and assignment operators • integer division can give floating point result • % coerces operands to integers • Usual set of mathematical functions • Other functions for things like formatting, type conversion, …

Booleans • False values are 0, 0.0, "0", "", false, NULL, array with 0 elements, object with 0 member variables • everything else is true • Usual set of comparison operators • (< <= == != >= >) • work with strings • Usual set of logical operators (! && ||) plus andorxor

Type Conversions • Coercion (automatic type conversion) happens based on context. It happens in more ways than in Java. • integer -> double • numeric, boolean -> string • double -> integer • numeric -> boolean • string -> numeric • Explicit type conversion (int)$sum intval($sum) settype($sum, "integer")

Selection if ( cond) { … } elseif (cond2) { …} … else { … } also switch Loops while (cond) { … } do { … } while( cond); for (init; cond; update) { … } foreach() { … } Control Statements

Declaring Functions • function functionName(paramList) { • /* code goes here */ } • paramList is comma-separated list of param names with optional default values • parameters with default values need to be at the end of the list • use return to return a value • functions can be nested in PHP

Calling Functions • functionName( argList) • argList is comma-separated list of expressions • number of arguments needs to match the number of parameters unless default values have been assigned • if the last n parameters have default values, you can omit the last 1, 2, .. n arguments • you can't skip a position in the argument list

Variable scope • Variables defined outside of any function are global • Variables defined inside a function are local to the function (as are parameters) • To use global variables in a function • get them from $GLOBALS, an array containing all global variables x = $GLOBALS['varname']; • use the global keyword to declare them to be global global $varname;

Compound Types in PHP • PHP has two compound types • Arrays -arrays in PHP are really ordered maps (hash tables) • multi-dimensional arrays are arrays whose elements are arrays • Objects - variables whose type is defined by a class

Arrays • An array consists of a collection of elements • each element has a key and a value (like a hash table) • arrays with only numeric keys are a special case • you can use arrays with numeric keys the same way you do an array in C or Java

Creating an array • Create dynamically by assigning values to elements • $veggie['corn'] = 'yellow'; • $dinner[0] = 'Lemon Chicken'; • Use the Array constructor • $veggie = array( 'corn' => 'yellow', 'beet' => 'red', 'carrot' => 'orange');

Creating a numeric array • Use array with just a list of values • keys will automatically be numbers (starting from 0) $dinner = ('Sweet Corn and Asparagus', 'Lemon Chicken', 'Spicy Eggplant'); • Add new elements to end of list by assigning with no index • $dinner[] = 'Braised Bamboo fungus';

Using arrays • count($arrayName) gives the number of elements in the array • implode(delim, array) creates a string from an array • $menu = implode( ', ', $dinner); • explode(delim, string) creates a numeric array from a string • $dinner = explode( ', ', $menu);

Sorting arrays • The array elements will be rearranged by these methods • sort()/rsort() sort by element values (ascending/descending) • keys become numeric • asort()/arsort() sort by element value, keeping keys and values together • ksort()/krsort() sort by key, keeping keys and values together

Looping with arrays • Use foreach to loop through elements of array foreach( $meal as $key => $value) print "$key $value\n"; foreach( $dinner as $dish) print "You can eat $dish.\n" • foreach goes through elements in order they were added to array • not necessarily numeric order

Using arrays as lists and stacks • The functions current, next, prev, reset (which take an array parameter) allow you to use an array like a linked list. • list order is the order of insertion • array_push and array_pop allow you to use an array for a stack

Classes and Objects • PHP supports object-oriented programming • Class is a template describing both data and operations • Method is a function defined in a class • Property is a variable defined in a class • Constructor is used to create instances (objects) • Static method doesn't need an object

Sample Class definition class Cart { var $items; // Items in our shopping cart // Add $num articles of $artnr to the cart function add_item($artnr, $num) { $this->items[$artnr] += $num;} // Take $num articles of $artnr out of the cart function remove_item($artnr, $num) { if ($this->items[$artnr] > $num) { $this->items[$artnr] -= $num; return true; } elseif ($this->items[$artnr] == $num) { unset($this->items[$artnr]); return true; } else { return false; } }

Constructors • Constructor is a method with the same name as the class • Use it to initialize properties class Item { var $catalogNum, $price; function Item($id='none', $cost='0.0') { $catalogNum=$id; $price = $cost; } … }

Using Objects • Use new to create objects • $myItem = new Item( 'AB234', 3.95); • Access methods and properties with -> operator • $charge = $myItem->price;

Regular Expressions • PHP has POSIX regular expressions built in • The PCRE module allows you to use Perl compatible regular expressions • preg_match takes a pattern and a string and returns true or false • preg_split takes a delimiter and a string and returns an array

Running Shell Commands • PHP provides the shell_exec() function for running an external program from the php program $filelist = shell_exec( 'ls'); • If you are passing form input on to another program, use escapeshellargs() to clean it up first

Extensions • The mycrypt extension to PHP provides a number of standard encryption algorithms • The Perl and Java extensions allow you to execute code written in those languages from your PHP program • PEAR is an extension that is useful for applications that use databases • more next time

Sources • Learning PHP 5 by David Sklar • Programming the World Wide Web by Robert Sebesta • Programming PHP by Rasmus Ledorf and Kevin Tatroe • PHP home page • http://www.php.net/

PHP

PHP

Presentation Transcript

PHP

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PHP PHP: Hypertext Preprocessing

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PHP PHP: Hypertext Preprocessing

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