PHP Tutorials - Herong's Tutorial Examples - Version 4.20, by Dr. Herong Yang
What Is a Function
This section describes what is a function. A quick example is provided showing how to define and call a function.
What Is a Function? A function is a definition of a block of statements. The block of statements in a function will be executed only when the function is invoked. PHP provides a long list of built-in (predefined) functions. PHP supports user-defined functions - You define your own functions in PHP source code.
To learn how to use user-defined functions in PHP, we need to pay attentions in following areas:
1. How to define a function?
2. How to call a function to execute its statements?
3. How to pass input values into a function?
4. How to return a result from a function?
5. How to share variables with a function?
Here is a simple example script of defining a function, calling a function, passing data into a function, and returning result from a function:
function square($x) { $y = $x * $x; return $y; } $radius = 2.0; $area = M_PI * square($radius); echo($area);
Notice that in this example script:
Last update: 2019.
Table of Contents
Introduction and Installation of PHP 7.3
PHP Data Types and Data Literals
Variables, References, and Constants
Expressions, Operations and Type Conversions
Conditional Statements - "if" and "switch"
Loop Statements - "while", "for", and "do ... while"
►Function Declaration, Arguments, and Return Values
"function" Statements - Defining Functions
Passing Arguments to Functions
Example of Passing Arguments by Values
Using Pass-by-Value Arguments for References
Example of Passing Arguments by References
Variable-Length Argument Lists
Providing Default Values to Argument Variables
Returning Values from Functions
Returning References from Functions
Introduction of Class and Object
Integrating PHP with Apache Web Server
Retrieving Information from HTTP Requests
Creating and Managing Sessions in PHP Scripts
Sending and Receiving Cookies in PHP Scripts
Controlling HTTP Response Header Lines in PHP Scripts
MySQL Server Connection and Access Functions
Functions to Manage Directories, Files and Images
SOAP Extension Function and Calling Web Services
SOAP Server Functions and Examples
Localization Overview of Web Applications
Using Non-ASCII Characters in HTML Documents
Using Non-ASCII Characters as PHP Script String Literals
Receiving Non-ASCII Characters from Input Forms
"mbstring" Extension and Non-ASCII Encoding Management
Managing Non-ASCII Character Strings with MySQL Servers