Variable-Length Argument Lists

This section provides a tutorial example on how to access arguments in a function without using argument variables and how to pass arguments more than what are defined in the function statement.

As I mentioned earlier, PHP also allows you to access arguments provided in the function call operation without using argument variables. Here is how:

1. func_get_arg(position) - It returns the value of the specified argument provided in the function call operation. "position" is the position index of the specified argument. The position index of the first argument is 0. For example, if "func_get_arg(2)" is used in a function, it will return the value of the 3rd argument.

2. func_num_args() - It returns the total number of arguments provided in the function call operation. For example, if "func_num_args()" returns 1, you know that there is only 1 argument provided by calling code.

3. func_get_args() - It creats and returns an array which contains values of all arguments provided in the function call operation. For example, if "$args = func_get_args()" is used in a function, $args will be array containing all arguments.

With all these 3 functions, we say that PHP supports variable-length argument lists with some basic rules:

To help us understand how use variable-length argument list feature, I wrote this tutorial example:

<?php # ArgumentList.php
#- Copyright (c) 2015, HerongYang.com, All Rights Reserved.
#
   function f2c($fahrenheit) {
      $celsius = (func_get_arg(0) - 32.0) / 1.8;
      return $celsius;
   }

   print("\n Calling a function that uses func_get_arg():\n");
   if (f2c(20.0)<0.0) print("    It's cold here!\n");
   
   function myMax() {
      $max = NULL; 
      if (func_num_args()>0) $max = func_get_arg(0);
      for ($i=1; $i<func_num_args(); $i++) {
         if ($max < func_get_arg($i)) $max = func_get_arg($i);
      }
      return $max;
   }

   print("\n Calling a function that uses func_num_args():\n");
   print("    ".myMax()."\n");
   print("    ".myMax(3)."\n");
   print("    ".myMax(3, 1, 4)."\n");
   print("    ".myMax(3, 1, 4, 1, 5, 9, 2, 6, 5)."\n");

   function myMin() {
      $list = func_get_args();
      $min = NULL;
      if (count($list)>0) $min = $list[0];
      for ($i=1; $i<count($list); $i++) {
         if ($min > $list[$i]) $min = $list[$i];
      }
      return $min;
   }

   print("\n Calling a function that uses func_get_args():\n");
   print("    ".myMin()."\n");
   print("    ".myMin(5)."\n");
   print("    ".myMin(5, 6, 2)."\n");
   print("    ".myMin(5, 6, 2, 9, 5, 1, 4, 1, 3)."\n");
?>

If you run this sample script, you should get:

 Calling a function that uses func_get_arg():
    It's cold here!

 Calling a function that uses func_num_args():

    3
    4
    9

 Calling a function that uses func_get_args():

    5
    2
    1

Last update: 2015.

Table of Contents

 About This Book

 Introduction and Installation of PHP 7.0

 PHP Script File Syntax

 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

 What Is a Function?

 "function" Statements - Defining Functions

 Function Call Operations

 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

 Arrays - Ordered Maps

 Configuring and Sending out Emails

 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

 Introduction of Class and Object

 Integrating PHP with Apache Web Server

 Outdated Tutorials

 References

 PDF Printing Version