Passing Objects as Function Arguments

This section describes how to pass objects as function arguments - There are two ways to pass an object into as a function argument: Pass-by-Value and Pass-by-Reference. They follow same rules as the assignment statement.

There are two ways to pass an object into as a function argument: Pass-by-Value and Pass-by-Reference. They follow same rules as the assignment statement.

1. Pass-by-Value - The function argument variable is declared as pass-by-value, which works like an assignment statement assigning the value of the calling expression to the argument variable. In other words, when the function is called, the calling statement provides a variable (or an expression) whose value is the identifier of the object, and a copy of the value is assigned to the function argument variable. For example:

   function f($aa) {...}
   $a = new C();
   f($a);
#     f() receives a copy of the value in $a similar to $aa=$a

2. Pass-by-Reference - The function argument variable is declared as pass-by-reference, which works like an assignment statement assigning the reference of the calling expression to the argument variable. In other words, when the function is called, the calling statement provides a variable (or an expression) whose value is the identifier of the object, and a reference to the variable is assigned to the function argument variable to make it as an alias of the variable. For example:

   function f(&$bb) {...}
   $b = new C();
   f($b);
#     f() receives a reference of $b similar to $bb=&$b

The tutorial example below shows how to pass objects as function arguments:

<?php 
/* PassingObjectAsArguments.php
#- Copyright (c) 2015-2019, HerongYang.com, All Rights Reserved.
*/
class C {
   public $size;
   public function __construct($s = "Medidum") {
      $this->size = $s;
   }
}

function updateObject($aa,&$bb) {
   $aa->size = "Large";
   $bb->size = "Large";
   return $aa;
}
function updateContent($aa,&$bb) {
   $aa = new C("Large");
   $bb = new C("Large");
   return $aa;
}

   echo "Test on updating object identified by variable content:\n";
   $a = new C();
   $b = new C();
   $z = updateObject($a,$b);
   echo "   a: ".$a->size."\n";
   echo "   b: ".$b->size."\n";
   echo "   z: ".$z->size."\n";

   echo "Test on updating variable content:\n";
   $a = new C();
   $b = new C();
   $z = updateContent($a,$b);
   echo "   a: ".$a->size."\n";
   echo "   b: ".$b->size."\n";
   echo "   z: ".$z->size."\n";
?>

If you run the above tutorial example, you will get something like this:

C:\herong> \php\php PassingObjectAsArguments.php

Test on updating object identified by variable content:
   a: Large
   b: Large
   z: Large
Test on updating variable content:
   a: Medidum
   b: Large
   z: Large

The output confirms the my understanding presented earlier.

Also note that:

Last update: 2019.

Table of Contents

 About This Book

 Introduction and Installation of PHP 7.3

 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

 Arrays - Ordered Maps

Introduction of Class and Object

 What Is a Class

 What Is an Object

 What Is a Constructor

 What Is a Static Method

 What Is a Static Variable

 What Is a Superclass and a Subclass

 What Is an Abstract Class

 What Is an Abstract Method

 What Is an Interface

 What Is a Trait

 What Is an Overloaded Property

 What Is an Overloaded Method

 What Is Object Property Iteration

 What Is Object Cloning

 What Is Object Serialization

 What Is in an Object Variable

 Updating Variables Who Share an Object

Passing Objects as Function Arguments

 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

 Configuring and Sending out Emails

 Outdated Tutorials

 References

 Full Version in PDF/EPUB