isset() function in PHP

By: Emiley J. Printer Friendly Format

isset() determines whether a certain variable has already been declared by PHP. It returns a boolean value true if the variable has already been set, and false otherwise, or if the variable is set to the value NULL.

Consider the following script:

if (isset($first_name)) {

print '$first_name is set';

}

This code snippet checks whether the variable $first_name is defined. If $first_name is defined, isset() returns true , which will display ' $first_name is set. ' If it isn’t, no output is generated.

isset() can also be used on array elements and object properties. Here are examples for the relevant syntax, which you can refer to later:.

Checking an array element:

if (isset($arr["offset"])) {

...

}

Checking an object property:

if (isset($obj->property)) {

...

}

Note that in both examples, we didn’t check if $arr or $obj are set (before we checked the offset or property, respectively). The isset() construct returns false automatically if they are not set.

isset() is the only one of the three language constructs that accepts an arbitrary amount of parameters. Its accurate prototype is as follows:

isset($var1, $var2, $var3, ...);

It only returns true if all the variables have been defined; otherwise, it returns false. This is useful when you want to check if the required input variables for your script have really been sent by the client, saving you a series of single isset() checks.

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1. Simple and straightforward. Thats what I like abou
View Tutorial By: Barand at 2009-03-21 11:03:47

2. Thanks, how about using isset() function on page/U
View Tutorial By: Paolo at 2009-06-01 07:29:10

3. Fine,you r very straightforward I like that

View Tutorial By: Shaiju at 2010-02-21 10:15:00

4. i can understand easily what is isset but i am not
View Tutorial By: sebestiraj at 2010-04-09 00:09:36

5. ds
View Tutorial By: sdsd at 2010-08-31 04:05:46

6. thanks i learnt how to use isset in php
View Tutorial By: free web directory at 2010-09-15 19:42:28

7. now I know what isset is for, thank you very much
View Tutorial By: Anonymous at 2010-12-23 20:43:29

8. I can't get it untill now. I need further explaina
View Tutorial By: johnlie at 2011-01-19 20:31:09

9. please give example code with defined variable.
View Tutorial By: shajjad at 2011-02-13 20:56:09

10. what about (!isset)?? the isset with "!"
View Tutorial By: bali web design at 2011-04-21 12:50:36

11. what about (!isset)?? the isset with "!"
View Tutorial By: bali web design at 2011-04-21 12:51:38

12. but need in the case of radio buttons
View Tutorial By: vishnu at 2011-07-21 11:39:26

13. this is very powerful document of isset method. th
View Tutorial By: mehul patel at 2011-08-29 12:16:48

14. Hello ,
I have a problem in understanding c
View Tutorial By: dimitra at 2011-10-05 16:24:11

15. It is so simple i like it,thnx...
View Tutorial By: Shahid Hussain at 2011-12-14 12:37:46

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View Tutorial By: dorji wangmo at 2011-12-27 05:38:35

17. so but I cannot use isset($var) instead of $var!=&
View Tutorial By: Dan at 2012-01-12 19:23:09

18. this is very helpful...
View Tutorial By: arrian at 2012-02-08 03:08:53

19. Thanks..
Short & Sweet Description.

View Tutorial By: Prashaad at 2012-02-23 17:37:14

20. Thanks ! very information full site
View Tutorial By: Kedar at 2012-04-22 08:53:17

21. my question is the same of sajjad.what about (!iss
View Tutorial By: hossain at 2012-04-26 04:28:56

22. The !isset() is basically checking if the string i
View Tutorial By: Bijan at 2012-09-21 20:49:41

23. I lik the description.
View Tutorial By: Praveen saini at 2012-11-05 10:13:41

24. if(isset($_POST["check1"]=="1"
View Tutorial By: krunal at 2012-11-22 10:30:19

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View Tutorial By: Logeswari at 2013-04-09 05:55:25

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View Tutorial By: Logeswari at 2013-04-30 10:46:54

27. how to use isset keyword with multidimensional arr
View Tutorial By: mehul at 2015-01-19 23:46:41

28. how to use isset keyword with multidimensional arr
View Tutorial By: mehul at 2015-01-19 23:47:02

29. Guestchoob
View Tutorial By: Guestchoob at 2017-03-02 05:59:38

30. KostyaExhat
View Tutorial By: KostyaExhat at 2017-06-16 09:47:59

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