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PHP: isset() function

isset() function

The isset () function is used to check whether a variable is set or not. If a variable is already unset with unset() function, it will no longer be set. The isset() function return false if testing variable contains a NULL value.

Version:

(PHP 4 and above)

Syntax:

isset(variable1, variable2......) 

Parameter:

Name Description Required /
Optional
Type
variable1 The variable being checked Required Mixed*
Variable2 ...... More variable to be checked. Optional Mixed*

*Mixed: Mixed indicates that a parameter may accept multiple (but not necessarily all) types.

Return value:

TRUE if variable (variable1,variable2..) exists and has value not equal to NULL, FALSE otherwise.

Value Type: Boolean.

Pictorial presentation of PHP isset() function

Pictorial presentation of PHP isset() function

Example:

<?php
$var1 = 'test';
var_dump(isset($var1));
?>

Output :

bool(true) 

View the example in the browser

Practice here online :

See also

PHP Function Reference