PHP Functions Composite Types

Functions  Declaration  function functionName(paramList) {  /* code goes here */ }  paramList is comma-separated list of param names with optional default values  use return to return a value  Calling a function  functionName( argList)  argList is comma-separated list of expressions - number must match declaration

Variable scope  Variables defined outside of any function are global  Variables defined inside a function are local to the function (as are parameters)  Using global variables in a function  $GLOBALS is array containing all global variables  global keyword

Compound Types in PHP  PHP has two compound types  Arrays -arrays in PHP are really ordered maps  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)  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

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;

Sources  Learning PHP 5 by David Sklar  Programming PHP by Rasmus Ledorf and Kevin Tatroe  PHP home page 