PHP define()Function
Examples
Define a case-sensitive constant:
<?php
define("GREETING","Hello you! How are you today?");
echo constant("GREETING");
?>
define("GREETING","Hello you! How are you today?");
echo constant("GREETING");
?>
Run Example »
Definition and Usage
The define() function defines a constant.
Constants are similar to variables, except that:
- After being set, the value of a constant cannot be changed
- Constant names do not need a leading dollar sign ($)
- Scope does not affect access to constants
- Constant values can only be strings and numbers
Syntax
define(name,value,case_insensitive)
| Parameter | Description |
|---|---|
| name | Required. Specifies the name of the constant. |
| value | Required. Specifies the value of the constant. PHP 7 supports arrays, as in the example below:
<?php
// PHP7+ 支持
define('ANIMALS', [
'dog',
'cat',
'bird'
]);
echo ANIMALS[1]; // 输出 "cat"
?>
|
| case_insensitive | Optional. Specifies whether the constant name is case-sensitive. Possible values:
|
Technical Details
| Return value: | Returns TRUE on success, or FALSE on failure. |
|---|---|
| PHP Version: | 4+ |
More Examples
Example
Define a case-insensitive constant:
<?php
define("GREETING","Hello you! How are you today?",TRUE);
echo constant("greeting");
?>
define("GREETING","Hello you! How are you today?",TRUE);
echo constant("greeting");
?>
Run Example »
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