PHP 5 Functions
The real power of PHP comes from its functions; it has more
than 1000 built-in functions.
PHP User Defined Functions
Besides the built-in PHP functions, we can create our own functions.A function is a block of statements that can be used repeatedly in a program.
A function will not execute immediately when a page loads.
A function will be executed by a call to the function.
Create a User Defined Function in PHP
A user defined function declaration starts with the word "function":Syntax
function functionName()
{
code to be executed;
}
Note: A function name can start with a letter or underscore
(not a number).Tip: Give the function a name that reflects what the function does!
 |
Function names are NOT case-sensitive. |
|---|
Example
<?php
function writeMsg() {
echo "Hello world!";
}
writeMsg(); // call the function
?>
PHP Function Arguments
Information can be passed to functions through arguments. An argument is just
like a variable.
Arguments are specified after the function name, inside the parentheses. You
can add as many arguments as you want, just separate them with a comma.
The following example has a function with one argument ($fname). When the
familyName() function is called, we also pass along a name (e.g. Jani), and the
name is used inside the function, which outputs several different first names,
but an equal last name:
Example
<?php
function familyName($fname) {
echo "$fname Refsnes.<br>";
}
familyName("Jani");
familyName("Hege");
familyName("Stale");
familyName("Kai Jim");
familyName("Borge");
?>
PHP Default Argument Value
The following example shows how to use a default parameter. If we call the
function setHeight() without arguments it takes the default value as argument:
Example
<?php
function setHeight($minheight = 50) {
echo "The height is :
$minheight <br>";
}
setHeight(350);
setHeight(); // will use
the default value of 50
setHeight(135);
setHeight(80);
?>
PHP Functions - Returning values
To let a function return a value, use the return statement:
Example
<?php
function sum($x, $y) {
$z = $x + $y;
return $z;
}
echo "5 + 10 = " . sum(5, 10) . "<br>";
echo "7 + 13 = " . sum(7, 13) .
"<br>";
echo "2 + 4 = " . sum(2, 4);
?>
PHP 5 Arrays
An array stores multiple values in one single variable:
Example
<?php
$cars = array("Volvo", "BMW", "Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>
What is an Array?
An array is a special variable, which can hold more than one value at a time.
If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:
$cars1 = "Volvo";
$cars2 = "BMW";
$cars3 = "Toyota";
However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?
The solution is to create an array!
An array can hold many values under a single name, and you can access the values by referring to an index number.
Create an Array in PHP
In PHP, the array() function is used to create an array:
array();
In PHP, there are three types of arrays:
- Indexed arrays - Arrays with a numeric index
- Associative arrays - Arrays with named keys
- Multidimensional arrays - Arrays containing one or more arrays
PHP Indexed Arrays
There are two ways to create indexed arrays:
The index can be assigned automatically (index
always starts at 0), like this:
$cars = array("Volvo", "BMW", "Toyota");
or the index can be assigned manually:
$cars[0] = "Volvo";
$cars[1] = "BMW";
$cars[2] = "Toyota";
The following example creates an indexed array named $cars, assigns three
elements to it, and then prints a text containing the array values:
Example
<?php
$cars = array("Volvo", "BMW", "Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>
Get The Length of an Array - The count() Function
The count() function is used to return the length (the number of elements) of
an array:
Example
<?php
$cars = array("Volvo", "BMW", "Toyota");
echo count($cars);
?>
Loop Through an Indexed Array
To loop through and print all the values of an indexed array, you could use a for loop, like this:
Example
<?php
$cars = array("Volvo", "BMW", "Toyota");
$arrlength = count($cars);
for($x = 0; $x < $arrlength; $x++) {
echo $cars[$x];
echo "<br>";
}
?>
PHP Associative Arrays
Associative arrays are arrays that use named keys that you assign to them.
There are two ways to create an associative array:
$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
or:
$age['Peter'] = "35";
$age['Ben'] = "37";
$age['Joe'] = "43";
Loop Through an Associative Array
To loop through and print all the values of an associative array, you could use a foreach loop, like this:
Example
<?php
$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
foreach($age as $x => $x_value) {
echo "Key=" . $x .
", Value=" . $x_value;
echo "<br>";
}
?>
PHP 5 Sorting Arrays
The elements in an array can be sorted in alphabetical or numerical order, descending or ascending.
PHP - Sort Functions For Arrays
In this chapter, we will go through the following PHP array sort functions:
- sort() - sort arrays in ascending order
- rsort() - sort arrays in descending order
- asort() - sort associative arrays in ascending order, according to the
value
- ksort() - sort associative arrays in ascending order, according to the
key
- arsort() - sort associative arrays in descending order, according to the
value
- krsort() - sort associative arrays in descending order, according to the
key
Sort Array in Ascending Order - sort()
The following example sorts the elements of the $cars array in ascending alphabetical order:
Example
<?php
$cars = array("Volvo", "BMW", "Toyota");
sort($cars);
?>
Example
<?php
$numbers = array(4, 6, 2, 22, 11);
sort($numbers);
?>
PHP 5 Global Variables - Superglobals
Superglobals were introduced in PHP 4.1.0, and are built-in
variables that are always available in all scopes.
PHP Global Variables - Superglobals
Several predefined variables in PHP are "superglobals", which means that they
are always accessible, regardless of scope - and you can access them from any
function, class or file without having to do anything special.
The PHP superglobal variables are:
- $GLOBALS
- $_SERVER
- $_REQUEST
- $_POST
- $_GET
- $_FILES
- $_ENV
- $_COOKIE
- $_SESSION
This chapter will explain some of the superglobals, and the rest will be
explained in later chapters.
PHP $GLOBALS
$GLOBALS is a PHP super global variable which is used to access
global variables from anywhere in the PHP script (also from within
functions or methods).
PHP stores all global variables in an array called $GLOBALS[index].
The index holds the name of the variable.
The example below shows how to use the super global variable $GLOBALS:
Example
<?php
$x = 75;
$y = 25;
function addition() {
$GLOBALS['z'] =
$GLOBALS['x'] + $GLOBALS['y'];
}
addition();
echo $z;
?>
PHP $_SERVER
$_SERVER is a PHP super global variable which holds information about headers,
paths, and script locations.
The example below shows how to use some of the elements in $_SERVER:
Example
<?php
echo $_SERVER['PHP_SELF'];
echo "<br>";
echo $_SERVER['SERVER_NAME'];
echo "<br>";
echo $_SERVER['HTTP_HOST'];
echo "<br>";
echo $_SERVER['HTTP_REFERER'];
echo "<br>";
echo
$_SERVER['HTTP_USER_AGENT'];
echo "<br>";
echo
$_SERVER['SCRIPT_NAME'];
?>
The following table lists the most important elements that can go inside $_SERVER:
Element/Code
Description
$_SERVER['PHP_SELF']
Returns the filename of the currently executing script
$_SERVER['GATEWAY_INTERFACE']
Returns the version of the Common Gateway Interface (CGI) the server is
using
$_SERVER['SERVER_ADDR']
Returns the IP address of the host server
$_SERVER['SERVER_NAME']
Returns the name of the host server (such as www.w3schools.com)
$_SERVER['SERVER_SOFTWARE']
Returns the server identification string (such as Apache/2.2.24)
$_SERVER['SERVER_PROTOCOL']
Returns the name and revision of the information protocol (such as HTTP/1.1)
$_SERVER['REQUEST_METHOD']
Returns the request method used to access the page (such as POST)
$_SERVER['REQUEST_TIME']
Returns the timestamp of the start of the request (such as 1377687496)
$_SERVER['QUERY_STRING']
Returns the query string if the page is accessed via a query string
$_SERVER['HTTP_ACCEPT']
Returns the Accept header from the current request
$_SERVER['HTTP_ACCEPT_CHARSET']
Returns the Accept_Charset header from the current request (such as
utf-8,ISO-8859-1)
$_SERVER['HTTP_HOST']
Returns the Host header from the current request
$_SERVER['HTTP_REFERER']
Returns the complete URL of the current page (not reliable because not all
user-agents support it)
$_SERVER['HTTPS']
Is the script queried through a secure HTTP protocol
$_SERVER['REMOTE_ADDR']
Returns the IP address from where the user is viewing the current page
$_SERVER['REMOTE_HOST']
Returns the Host name from where the user is viewing the current page
$_SERVER['REMOTE_PORT']
Returns the port being used on the user's machine to communicate with the
web server
$_SERVER['SCRIPT_FILENAME']
Returns the absolute pathname of the currently executing script
$_SERVER['SERVER_ADMIN']
Returns the value given to the SERVER_ADMIN directive in the web server
configuration file (if your script runs on a virtual host, it will be the value
defined for that virtual host) (such as someone@w3schools.com)
$_SERVER['SERVER_PORT']
Returns the port on the server machine being used by the web server for
communication (such as 80)
$_SERVER['SERVER_SIGNATURE']
Returns the server version and virtual host name which are added to
server-generated pages
$_SERVER['PATH_TRANSLATED']
Returns the file system based path to the current script
$_SERVER['SCRIPT_NAME']
Returns the path of the current script
$_SERVER['SCRIPT_URI']
Returns the URI of the current page
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