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Introduction to Functions and Arrays

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PHP Fundamentals: Functions

A set of constructs which allow the programmer to break up their code into smaller, more manageable, chunks which can be called by name and which may or may not return a value.

function function_name (parameters) { function-body }

function helloWorld(){echo "HelloWorld"; //No out put is shown

}


Functions: Passing Parameters

Passing parameters by value– function salestax($price,$tax) {

$total = $price + ($price * $tax echo "Total cost: $total"; } salestax(15.00,.075);

$pricetag = 15.00; $salestax = .075;

salestax($pricetag, $salestax);


Functions: Passing Parameters

Passing parameters by reference $cost = 20.00; $tax = 0.05; function calculate_cost(&$cost, $tax) { // Modify the $cost variable $cost = $cost + ($cost * $tax); // Perform some random change to the $tax variable. $tax += 4; } calculate_cost($cost,$tax); echo "Tax is: ". $tax*100."<br />"; echo "Cost is: $". $cost."<br />";


Functions: Default Argument Values

Default values are automatically assigned to the argument if no other value is provided

function salestax($price,$tax=.0575) { $total = $price + ($price * $tax); echo "Total cost: $total";

}

$price = 15.47;salestax($price);


Functions: Optional Arguments

Certain arguments can be designated as optional by placing them at the end of the list and assigning them a default value of nothing .

function salestax($price, $tax="") { $total = $price + ($price * $tax); echo "Total cost: $total";

}

salestax(42.00);

function calculate($price,$price2="",$price3="") { echo $price + $price2 + $price3; }

calculate(10,"", 3);


Functions: Returning Values from a Function

You can pass data back to the caller by way of the return keyword.

function salestax($price,$tax=.0575) { $total = $price + ($price * $tax); return $total;

} $total = salestax(6.50); Returning Multiple Values

function retrieve_user_profile() { $user[] = "Jason"; $user[] = "[email protected]";

return $user; } list($name,$email) = retrieve_user_profile(); echo "Name: $name, email: $email ";


Functions: Nesting Functions

defining and invoking functions within functions

function salestax($price,$tax) function convert_pound($dollars, $conversion=1.6) { return $dollars * $conversion; }

$total = $price + ($price * $tax); echo "Total cost in dollars: $total. Cost in British pounds: " . convert_pound($total);

}

salestax(15.00,.075);echo convert_pound(15);


Functions: Recursive Functions

functions that call themselves

function nfact($n) { if ($n == 0) { return 1;

}else { return $n * nfact($n - 1); } } //call to function

nfact($num) ;


Functions: Variable Functions

Functions with parameters on run time

function hello(){if (func_num_args()>0){

$arg=func_get_arg(0); //Thefirstargumentisatposition0echo "Hello$arg";

} else {echo "HelloWorld";

}}hello("Reader"); //Displays"HelloReader"hello(); //Displays"HelloWorld"


Server Side Includes (SSI): include() function

Include function You can insert the content of one PHP file into another PHP file before the server

executes it, with the include() or require() function. (e.g. Header, Menu, footer) The include() function takes all the content in a specified file and includes it in the

current file include() generates a warning, but the script will continue execution

<html><body><?php include("header.php"); ?><h1>Welcome to my home page!</h1><p>Some text.</p></body></html>



<html> <body> <div class="leftmenu"> <?php include("menu.php"); ?> </div> <h1>Welcome to my home page.</h1> <p>Some text.</p> </body> </html>



<html><body><div class="leftmenu"><a href="/default.php">Home</a><a href="/tutorials.php">Tutorials</a><a href="/references.php">References</a><a href="/examples.php">Examples</a> <a href="/about.php">About Us</a> <a href="/contact.php">Contact Us</a></div><h1>Welcome to my home page!</h1><p>Some text.</p></body></html>


Server Side Includes (SSI): require() function

Require function require() generates a fatal error, and the script will stop

include() generates a warning, but the script will continue execution

<html> <body> <?php require("wrongFile.php"); echo "Hello World!"; ?> </body> </html> It is recommended to use the require() function instead of include(), because

scripts should not continue after an error.


PHP Built In Functions

Math functions

http://www.w3schools.com/php/php_ref_math.asp– pi() Returns the value of PI – pow() Returns the value of x to the power of y– rad2deg() Converts a radian number to a degree– rand() Returns a random integer– round() Rounds a number to the nearest integer– sin() Returns the sine of a number– sinh() Returns the hyperbolic sine of a number– sqrt() Returns the square root of a number– srand() Seeds the random number generator– tan() Returns the tangent of an angle– tanh()– abs() Returns the absolute value of a number


PHP Built In Misc. Functions

Constants

– M_LN10 Returns the natural logarithm of 10 (approx. 2.302)– M_PI Returns PI (approx. 3.14159)– M_SQRT2 Returns the square root of 2 (approx. 1.414)

Miscellaneous Functions

– Strlen Returns length of a string – count() Returns the count of an array.– Strtolower strtolower() to lower case.– strtoupper() strtoupper() convert string to upper case


PHP Fundaments - Arrays

Arrays are ordered collections of items, called elements

Each element has a value, and is identified by a key that is unique to the array It belongs to

In PHP, there are three kind of arrays:– Numeric array - An array with a numeric index– Associative array - An array where each ID key is associated with a value– Multidimensional array - An array containing one or more arrays.

– $a = array();– $state[0] = "Delaware";– $a = array (10, 20, 30);– $a = array (’a’ => 10, ’b’ => 20, ’cee’ => 30);– $a = array (5 => 1, 3 => 2, 1 => 3,);



Numeric Arrays:– A numeric array stores each array element with a numeric index.– $cars = array("Saab","Volvo","BMW","Toyota");– $cars[0]="Saab"; //2nd way of declaring arrays– $cars[1]="Volvo";– $cars[2]="BMW";– $cars[3]="Toyota";– echo $cars[0] . " and " . $cars[1] . " are Swedish cars.";

Associative Arrays– An associative array, each ID key is associated with a value.– $ages = array(«John"=>32, «Jane"=>30, «David"=>34);

– $ages[‘John '] = "32";– $ages[‘Jane '] = "30";– $ages[‘David '] = "34";– $states = array (0 => "Alabama", "1" => "Alaska"..."49" => "Wyoming"); //numeric– $states = array ("OH" => "Ohio", "PA" => "Pennsylvania", "NY" => "New York")



Multidimensional Arrays Arrays of arrays, known as multidimensional arrays In a multidimensional array, each element in the main array can also be an array. $cars = array ( “Toyota"=>array ( “Corolla“, " Camry“, "Toyota 4Runner” ), “Suzuki"=>array ( “Vitara” ), “Honda"=>array ( "Accord“, “Sedan“, “Odyssey” ) );

echo "Is " . $ cars [Toyota '][2] . " a member of the Toyota cars?“; Is Toyota 4Runner a member of the Toyota cars?

$states = array ( "Ohio" => array ("population" => "11,353,140", "capital" => "Columbus"), "Nebraska" => array ("population" => "1,711,263", "capital" => "Omaha"))


PHP Fundaments – Printing Arrays

print_r() and var_dump()

var_dump– var_dump() outputs the data types of each value– var_dump() is capable of outputting the value of more than one variable– var_dump($states);– $a = array (1, 2, 3);– $b = array (’a’ => 1, ’b’ => 2, ’c’ => 3);– var_dump ($a + $b); // creates union of arrays– If 2 arrays have common elements and also share same string or numeric key will

appearance in result or output print_r

– print_r can return its output as a string, as opposed to writing it to the script’s standard output

– print_r($states);


PHP Fundaments – Comparing - Counting Arrays

$a = array (1, 2, 3); $b = array (1 => 2, 2 => 3, 0 => 1); $c = array (’a’ => 1, ’b’ => 2, ’c’ => 3); var_dump ($a == $b); // True var_dump ($a === $b); // False returns true only if the array contains the same key/value pairs in the same order

var_dump ($a == $c); // True var_dump ($a === $c); // False

$a = array (1, 2, 4); $b = array(); $c = 10; echo count ($a); // Outputs 3 echo count ($b); // Outputs 0 echo count ($c); // Outputs 1 is_array() function : echo in_array ($a, 2); // True


PHP Fundaments – Flipping and Reversing , Range

array_flip() – Exchanges all keys with their associated values in an array

$trans = array("a" => 1, "b" => 1, "c" => 2);$trans = array_flip($trans);print_r($trans);

– Output = Array ( [1] => b [2] => c ) array_reverse()

– Return an array with elements in reverse order array_values()

– array_values — Return all the values of an array– $array = array("size" => "XL", "color" => "gold");

print_r(array_values($array)); – array_keys — Return all the keys of an array

range()– The range() function provides an easy way to quickly create and fill an array consisting

of a range of low and high integer values.– $die = range(0,6); // Same as specifying $die = array(0,1,2,3,4,5,6)

By ProgrammerBlog.net http://programmerblog.net/By ProgrammerBlog.net http://programmerblog.net/

PHP Fundaments – Sorting Arrays

There are many functions in PHP core that provide various methods of sorting array contents.

sort– $array = array(’a’ => ’foo’, ’b’ => ’bar’, ’c’ => ’baz’);

sort($array); var_dump($array);

asort //to maintain key association, - $array = array(’a’ => ’foo’, ’b’ => ’bar’, ’c’ => ’baz’);

asort($array); var_dump($array);

rsort, arsort // sorting an array in descending order


PHP Fundaments – Arrays as Stack and Queues

Stack Last in First Out. array_push()

– $stack = array(); array_push($stack, ’bar’, ’baz’);

var_dump($stack); array_pop()

– $states = array("Ohio","New York","California","Texas");– $state = array_pop($states); // $state = "Texas"

Queues array_shift, Shift an element off the beginning of array array_unshift - Prepend one or more elements to the beginning of an array

$stack = array(’qux’, ’bar’, ’baz’);$first_element = array_shift($stack);

var_dump($stack); array_unshift($stack, ’foo’);

var_dump($stack);


Super Globals

Several predefined variables in PHP are "superglobals", which means they are available in all scopes throughout a script. There is no need to do global $variable; to access them within functions or methods.

$GLOBALS $_SERVER $_GET $_POST $_FILES $_COOKIE $_SESSION $_REQUEST $_ENV


http://www.php.net/manual/en/reserved.variables.globals.php

http://www.php.net/manual/en/reserved.variables.server.php

http://www.php.net/manual/en/reserved.variables.get.php

http://www.php.net/manual/en/reserved.variables.post.php

http://www.php.net/manual/en/reserved.variables.files.php

http://www.php.net/manual/en/reserved.variables.cookies.php

http://www.php.net/manual/en/reserved.variables.session.php

http://www.php.net/manual/en/reserved.variables.request.php

http://www.php.net/manual/en/reserved.variables.environment.php

Features – Super Globals

$GLOBALS — References all variables available in global scope <?php

function test() { $foo = "local variable";

echo '$foo in global scope: ' . $GLOBALS["foo"] . "\n"; echo '$foo in current scope: ' . $foo . "\n";}

$foo = "Example content";test();?>

$_SERVER -- $HTTP_SERVER_VARS [deprecated] — Server and execution environment information

<?phpecho $_SERVER['SERVER_NAME'];?>


Super Globals

$_ENV -- $HTTP_ENV_VARS [deprecated] — Environment variables <?php

echo 'My username is ' .$_ENV["USER"] . '!';?>

$ip = $_SERVER['REMOTE_ADDR'];


Super Globals

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