AIHOST™ PHP Tutorial 4

PHP Tutorial

How do I create a constant using PHP?
A constant is a name that represents a value you want to remain the same throughout a PHP script. Regardless of where a constant is created in a PHP script, the constant can be accessed anywhere in the script.

The define function is used to create a constant in your script. The name of the constant you want to create must be specified first. Constant names must start with a letter or an underscore (_) character. To help distinguish constants from variable, you should use all uppercase letters in a constant name. The name of the constant must be enclosed in quotation marks (" ") when specified in the define function. An example is below:

<html>
<head>
<title>User-defined Constants</title>
</head>
<body>
<? //creates a constant
define("AUTHOR", "Author Name");
print "This page was created by ";
print AUTHOR; //The output will be: This page was created by Author Name
?>
</body>
</html>

Escape Sequence Description

__FILE__ Returns the filename of the script being processed.

__LINE__ Returns the number of the line being processed in the script.

PHP_VERSION Returns the version number of PHP being used.

PHP_OS Returns the name of the operation system running PHP.

TRUE Stores a value of true

FALSE Stores a value of false. related to parsing.

E_ERROR Indicates a fatal error that is not related to parsing.

E_WARNING Indicates that an error has occurred, but PHP will continue processing the script.

E_PARSE Indicates a fatal parsing error caused by invalid syntax in the script.

E_NOTICE Indicates that an error may have occurred, but PHP will continue processing the script.

E_ALL Represents all the E_* constants. If used with the error_reporting function, all problems noticed by PHP will be reported.
NULL Represents no value.