PHP Tutorials - Herong's Tutorial Examples - v5.17, by Herong Yang
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 2015 (c) 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:
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:
Table of Contents
Introduction and Installation of PHP
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
Interface with Operating System
►Introduction of Class and Object
What Is a Superclass and a Subclass
What Is an Overloaded Property
What Is Object Property Iteration
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
Parsing and Managing HTML Documents
Configuring and Sending Out Emails
Managing PHP Engine and Modules on macOS