PHP Tutorials - Herong's Tutorial Examples
Dr. Herong Yang, Version 3.10

Data Literals Supported in PHP

This section describes data literals to specify values for different data types: reserved key words; decimal, octal and hexadecimal numbers; floating point number format; single quoted, double quoted, and heredoc strings.

Data literals are ways to provide values for different data types in PHP source code. PHP data literals rules are summarized below:

1. boolean data literals: Data literals for boolean data type are two reserved key words: true and false. Note that true and false are case in-sensitive - TRUE and FALSE are also valid boolean literals.

2. integer data literals: Data literals for integer data type have 3 forms:

  • Decimal form: A sequence of decimal digits, 0 to 9, with the first digit being > 0. Integer data literals in decimal form can be prefixed with or without positive or negative signs. For example: 366, -42, 6371, ...
  • Octal form: A sequence of octal digits, 0 to 7, with the first digit being 0. Integer data literals in octal form can be prefixed with or without positive or negative signs. For example: 0556, -052, 014343, ...
  • Hexadecimal form: 0x followed by a sequence of hexadecimal digits, 0 to 9 and A to F, with the first digit being 0. Integer data literals in hexadecimal form can be prefixed with or without positive or negative signs. For example: 0x16E, -0x2A, 0x18E3, ...

3. float data literals: Data literals for float data type are numeric values represented in signs and decimal digits with a decimal point and or exponential part. For example: 3.14159, 3e8, -1.25e-2, ...

4. string data literals: Data literals for string data type have 3 forms:

  • Singled quoted form: A sequence of 8-bit characters enclosed in a pair of single quotes ''. String data literals in single quoted form are subject to 2 escape sequences (backslash substitutions), \' and \\, to represent ' and \. For example: 'Today\'s Special:', 'Item Price Unit', 'Apples 3.49 kg', ...
  • Double quoted form: A sequence of 8-bit characters enclosed in a pair of double quotes "". String data literals in double quoted form are subject to a different set of escape sequences (backslash substitutions): \", \\, \t, \r, \n, \$, \ddd and \xHH. \ddd is used to represent any character in its octal value. \xHH is used to represent any character in its hexadecimal value. String data literals in double quoted form are also subject to variable substitutions: $variableName. For example: "Today's Special:", "Item\tPrice\tUnit", "Apples\t3.49\t\x6B\x67", "Eggs\t$price\tdoz\145\156", ...
  • Heredoc form: <<< followed by an identifier and a new line, then a sequence of 8-bit characters in one or more lines, and then the same identifier to end the literal. See the example given in the tutorial script below.
$monthDays = array("Jan"=>31,"Feb"=>28,"Mar"=>31);

5. array data literals: There are no data literals for array data type. Arrays are created by using the array constructor, array() function, or the array element notation, $arrayName[$key].

6. object data literals: There are no data literals for object data type. Objects are created by class constructors.

7. resource data literals: There are no data literals for resource data type. Resources are created by using PHP built-in functions.

8. null data literal: Data literal for null data type is 1 reserved key words: null. Note that null is case in-sensitive - NULL is the same as null.

Last update: 2005.

Table of Contents

 About This PHP Tutorial Book

 Introduction and Installation of PHP 5.4.3

 PHP Script File Syntax

PHP Data Types and Data Literals

 Data Types Supported in PHP

Data Literals Supported in PHP

 Data Literals Examples for Integer, String and Other Data Types

 Overflow of Integer and Float Values

 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

 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

 Outdated Tutorials

 References

 PDF Printing Version

Dr. Herong Yang, updated in 2012
Data Literals Supported in PHP