- PHP Tutorial
- PHP - Home
- PHP - Introduction
- PHP - Installation
- PHP - History
- PHP - Features
- PHP - Syntax
- PHP - Hello World
- PHP - Comments
- PHP - Variables
- PHP - Echo/Print
- PHP - var_dump
- PHP - $ and $$ Variables
- PHP - Constants
- PHP - Magic Constants
- PHP - Data Types
- PHP - Type Casting
- PHP - Type Juggling
- PHP - Strings
- PHP - Boolean
- PHP - Integers
- PHP - Files & I/O
- PHP - Maths Functions
- PHP - Heredoc & Nowdoc
- PHP - Compound Types
- PHP - File Include
- PHP - Date & Time
- PHP - Scalar Type Declarations
- PHP - Return Type Declarations
- PHP Operators
- PHP - Operators
- PHP - Arithmatic Operators
- PHP - Comparison Operators
- PHP - Logical Operators
- PHP - Assignment Operators
- PHP - String Operators
- PHP - Array Operators
- PHP - Conditional Operators
- PHP - Spread Operator
- PHP - Null Coalescing Operator
- PHP - Spaceship Operator
- PHP Control Statements
- PHP - Decision Making
- PHP - If…Else Statement
- PHP - Switch Statement
- PHP - Loop Types
- PHP - For Loop
- PHP - Foreach Loop
- PHP - While Loop
- PHP - Do…While Loop
- PHP - Break Statement
- PHP - Continue Statement
- PHP Arrays
- PHP - Arrays
- PHP - Indexed Array
- PHP - Associative Array
- PHP - Multidimensional Array
- PHP - Array Functions
- PHP - Constant Arrays
- PHP Functions
- PHP - Functions
- PHP - Function Parameters
- PHP - Call by value
- PHP - Call by Reference
- PHP - Default Arguments
- PHP - Named Arguments
- PHP - Variable Arguments
- PHP - Returning Values
- PHP - Passing Functions
- PHP - Recursive Functions
- PHP - Type Hints
- PHP - Variable Scope
- PHP - Strict Typing
- PHP - Anonymous Functions
- PHP - Arrow Functions
- PHP - Variable Functions
- PHP - Local Variables
- PHP - Global Variables
- PHP Superglobals
- PHP - Superglobals
- PHP - $GLOBALS
- PHP - $_SERVER
- PHP - $_REQUEST
- PHP - $_POST
- PHP - $_GET
- PHP - $_FILES
- PHP - $_ENV
- PHP - $_COOKIE
- PHP - $_SESSION
- PHP File Handling
- PHP - File Handling
- PHP - Open File
- PHP - Read File
- PHP - Write File
- PHP - File Existence
- PHP - Download File
- PHP - Copy File
- PHP - Append File
- PHP - Delete File
- PHP - Handle CSV File
- PHP - File Permissions
- PHP - Create Directory
- PHP - Listing Files
- Object Oriented PHP
- PHP - Object Oriented Programming
- PHP - Classes and Objects
- PHP - Constructor and Destructor
- PHP - Access Modifiers
- PHP - Inheritance
- PHP - Class Constants
- PHP - Abstract Classes
- PHP - Interfaces
- PHP - Traits
- PHP - Static Methods
- PHP - Static Properties
- PHP - Namespaces
- PHP - Object Iteration
- PHP - Encapsulation
- PHP - Final Keyword
- PHP - Overloading
- PHP - Cloning Objects
- PHP - Anonymous Classes
- PHP Web Development
- PHP - Web Concepts
- PHP - Form Handling
- PHP - Form Validation
- PHP - Form Email/URL
- PHP - Complete Form
- PHP - File Inclusion
- PHP - GET & POST
- PHP - File Uploading
- PHP - Cookies
- PHP - Sessions
- PHP - Session Options
- PHP - Sending Emails
- PHP - Sanitize Input
- PHP - Post-Redirect-Get (PRG)
- PHP - Flash Messages
- PHP AJAX
- PHP - AJAX Introduction
- PHP - AJAX Search
- PHP - AJAX XML Parser
- PHP - AJAX Auto Complete Search
- PHP - AJAX RSS Feed Example
- PHP XML
- PHP - XML Introduction
- PHP - Simple XML Parser
- PHP - SAX Parser Example
- PHP - DOM Parser Example
- PHP Login Example
- PHP - Login Example
- PHP - Facebook Login
- PHP - Paypal Integration
- PHP - MySQL Login
- PHP Advanced
- PHP - MySQL
- PHP.INI File Configuration
- PHP - Array Destructuring
- PHP - Coding Standard
- PHP - Regular Expression
- PHP - Error Handling
- PHP - Try…Catch
- PHP - Bugs Debugging
- PHP - For C Developers
- PHP - For PERL Developers
- PHP - Frameworks
- PHP - Core PHP vs Frame Works
- PHP - Design Patterns
- PHP - Filters
- PHP - JSON
- PHP - Exceptions
- PHP - Special Types
- PHP - Hashing
- PHP - Encryption
- PHP - is_null() Function
- PHP - System Calls
- PHP - HTTP Authentication
- PHP - Swapping Variables
- PHP - Closure::call()
- PHP - Filtered unserialize()
- PHP - IntlChar
- PHP - CSPRNG
- PHP - Expectations
- PHP - Use Statement
- PHP - Integer Division
- PHP - Deprecated Features
- PHP - Removed Extensions & SAPIs
- PHP - PEAR
- PHP - CSRF
- PHP - FastCGI Process
- PHP - PDO Extension
- PHP - Built-In Functions
- PHP Useful Resources
- PHP - Questions & Answers
- PHP - Quick Guide
- PHP - Useful Resources
- PHP - Discussion
PHP - isset() Function
Definition and Usage
The function isset() is used to determine is a variable is set/declared and is not null.
If a variable has been unset with the unset() function, it is no longer considered to be set.
Syntax
bool isset ( mixed $var , mixed ...$vars )
Parameters
Sr.No | Parameter & Description |
---|---|
1 | var Mandatory. The variable to be checked. |
2 |
vars Optional. Further variables. |
Return Values
This function returns true if var exists and has any value other than null. false otherwise.
This function will return false when checking a variable that has been assigned to null. A null character ("\0") is not equivalent to the PHP null constant.
If multiple parameters are supplied then isset() will return true only if all of the parameters are considered set. Evaluation goes from left to right and stops as soon as an unset variable is encountered.
Dependencies
PHP 4 and above
Example
Following example demonstrates use of function isset() −
<?php $a = ""; echo "a is ".( isset($a)? 'set' : 'not set') . "<br>"; $b = "test"; echo "b is ".( isset($b)? 'set' : 'not set') . "<br>"; $c = "test2"; echo "checking b and c are ".( isset($b,$c)? 'set' : 'not set') . "<br>"; echo "****after unset b**** <br>"; unset ($b); echo "b is ".( isset($b)? 'set' : 'not set') . "<br>"; echo "checking b and c are ".( isset($b,$c)? 'set' : 'not set') . "<br>"; $d = 1; echo "d is ".( isset($d)? 'set' : 'not set') . "<br>"; $e = NULL; echo "e is ".( isset($e)? 'set' : 'not set') . "<br>"; $f = array('a' => 'apple'); echo "f is ".( isset($f)? 'set' : 'not set') . "<br>"; $g = new stdClass(); echo "g is ".( isset($g)? 'set' : 'not set') . "<br>"; $h = ''; echo "h is ".( isset($h)? 'set' : 'not set') . "<br>"; ?>
Output
This will produce following result −
a is set b is set checking b and c are set ****after unset b**** b is not set checking b and c are not set d is set e is not set f is set g is set h is set
To Continue Learning Please Login
Login with Google