PHP functions define () and defined ()

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• Example 1
• Example 2

Define () Definition and usage:

The define () function defines a constant.

Constants are similar to variables, except that:

• After setting, the constant value cannot be changed.
• The constant name does not need to start with the dollar sign ($)
• The scope does not affect constant access.
• A constant value can only be a string or number.

Syntax:

 
Define (name, value, case_insensitive)
 

Parameters	Description
Name	Required. Specifies the name of a constant.
Value	Required. Specifies the value of a constant.
Case_insensitive	Required. Specifies whether the constant name is case sensitive. If it is set to true, it is not case sensitive. The default value is false (case sensitive ).

Example 1

Defines a case-sensitive constant:

<?PHPDefine("Greeting", "Hello world! ");Echo Constant("Greeting");?>
 

Output:

 
Hello world!
 

Example 2

Defines a case-insensitive constant:

 
<?PHPDefine("Greeting", "Hello world! ",True);Echo Constant("Greeting");?>
 

Output:

Hello world!

**************************************** **************************************** **************************************** ********************


Defined () Definition and usage:
 

The defined () function checks whether a constant exists.

If a constant exists, true is returned; otherwise, false is returned.

Syntax:

 
Defined (name)

 

Parameters	Description
Name	Required. Specifies the name of the constant to be checked.

 


Example:
 

<?PHPDefine("Greeting", "Hello world! ");Echo Defined("Greeting");?>
 

Output:

 
1