What Is an Array

This section describes what is an array - an ordered pairs of keys and values. If sequential integer keys are used, an array is a simple indexed list. If string keys are used, an array is a map.

What Is an Array? An array is a data type that represents an ordered pairs of keys and values. Arrays in PHP are different than arrays in most of other languages. Basic rules for PHP's arrays are:

1. An array can be constructed by the array constructor, like:

   $myArray = array(k1=>v1, k2=>v2, ..., kn=>vn);

where k1, k2, ..., and kn are keys of integer type or string type. v1, v2, ..., and vn are values of any data types.

2. The value of a given key in an array can be expressed by the array variable followed by the key in square brackets, like:

   print $myArray[kn];

3. The value of a given key in an array can be modified by an assignment statement, like:

   $myArray[kn] = new_value.

4. A new pair of key and value can be added to an array by an assignment statement, like:

   $myArray[kx] = vx

5. If a string key represents an integer, it will be used as an integer key. So $myArray['7'] is the same as $myArray[7].

6. If the key is missing in an array assignment or an array constructor, an integer key of 0, or the highest integer key plus 1, will be provided. So $myArray[] = "Last" assigns "Last" to a new integer key.

7. An empty string is also a valid string key, like:

   $myArray[''] = vy;

8. A pair of key and value can be removed by using the unset() function, like:


9. Pairs of keys and values are ordered in an array like a queue. New pairs are always added at the end of the array.

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

What Is an Array

 Creating Arrays - Examples

 Array Related Built-in Functions

 Usage Examples of Array Functions

 Interface with Operating System

 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

 Managing File Upload

 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

 Image and Picture Processing

 Managing ZIP Archive Files

 Managing PHP Engine and Modules on macOS

 Managing PHP Engine and Modules on CentOS

 Outdated Tutorials


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