The isset Construct
The isset construct checks whether a variable exists and whether its value is not null. Returns true if the variable exists and is not equal to null, otherwise returns false. Can accept multiple parameters - in this case, it will return true only if all passed variables exist.
Syntax
isset($var);
isset($var1, $var2, ...);
Example
Check if a variable exists:
<?php
$var = 'test';
var_dump(isset($var));
?>
Code execution result:
true
Example
Check multiple variables:
<?php
$a = 1;
$b = null;
var_dump(isset($a, $b));
?>
Code execution result:
false
Example
Check a non-existent variable:
<?php
var_dump(isset($undefinedVar));
?>
Code execution result:
false
