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PHP Tutorial

PHP Introduction

PHP 5 Installation

PHP 5 Syntax

PHP 5 Variables

PHP 5 echo and print Statements

PHP 5 Data Types

PHP 5 String Functions

PHP 5 Constants

PHP Arithmetic Operators

PHP 5 if...else...elseif Statements

PHP 5 switch Statement

PHP 5 while Loops

PHP 5 for Loops

PHP 5 Functions

PHP 5 Arrays

PHP 5 Sorting Arrays

PHP 5 Superglobals

PHP Forms

PHP 5 Form Handling

PHP 5 Form Validation

PHP 5 Forms - Required Fields

PHP 5 Forms E-mail /URL

PHP Form Complete

PHP Advanced

PHP 5 Multidimensional Arrays

PHP 5 Date and Time

PHP Include Files

PHP File Handling

PHP File Open/Read

PHP File Create/Write

PHP File Upload

PHP Cookies

PHP Sessions

PHP E-mail

PHP Secure E-mails

PHP Error Handling

PHP Exception Handling

PHP Filter

PHP Database

PHP MySQL Introduction

PHP MySQL Connect

PHP Create DB/Tables

PHP MySQL Insert Into

PHP MySQL Select


PHP Order By

PHP Update

PHP Delete



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":


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.

In the example below, we create a function named "writeMsg()". The opening curly brace ( { ) indicates the beginning of the function code and the closing curly brace ( } ) indicates the end of the function. The function outputs "Hello world!". To call the function, just write its name:


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 seperate 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:


function familyName($fname) {
  echo "$fname Refsnes.<br>";

familyName("Kai Jim");

The following example has a function with two arguments ($fname and $year):


function familyName($fname,$year) {
  echo "$fname Refsnes. Born in $year <br>";

familyName("Kai Jim","1983");

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:


function setHeight($minheight=50) {
  echo "The height is : $minheight <br>";

setHeight(); // will use the default value of 50

PHP Functions - Returning values

To let a function return a value, use the return statement: 


function sum($x,$y) {
  return $z;

echo "5 + 10 = " . sum(5,10) . "<br>";
echo "7 + 13 = " . sum(7,13) . "<br>";
echo "2 + 4 = " . sum(2,4);