What is isset function in php

What is the use of ‘isset’ in PHP?

: It is an optional value/values or variable/variables to check How does isset() Function works in PHP The isset() function works by returning the value TRUE if the $variable exists in the isset() function (isset() programming code) which has the value which is other than NULL value. If the isset() function will return/print the value “FALSE” if the isset() returns FALSE value.

What is the use of ‘isset’ in PHP?

if (isset($_GET[‘user_name’]) && !empty($_GET[‘user_name’]))

In the above code what is the use of the part — (isset($_GET[‘user_name’])

isset will check if $_GET[‘user_name’] is set and is not NULL . But if you are using !empty($_GET[‘user_name’]) , there is no need for isset() as empty() will take care of it.

Only if (!empty($_GET[‘user_name’])) will check if $_GET[‘user_name’] is set and it contains a value.

NOTE: empty() will return true for —

• «» (an empty string)
• 0 (0 as an integer)
• 0.0 (0 as a float)
• «0» (0 as a string)
• NULL
• FALSE
• array() (an empty array)
• $var; (a variable declared, but without a value)

PHP isset() Function, The isset () function checks whether a variable is set, which means that it has to be declared and is not NULL. This function returns true if the variable exists and is not NULL, otherwise it returns false. Note: If multiple variables are supplied, then this function will return true only if all of the variables are set.

What is Isset function in PHP

1 : What is isset () function in php2 :how to use isset () function in php3 :syntax of isset function of php all the above questions will be cleared in this vi

Isset() Function in PHP

Introduction to isset() Function in PHP

The isset() function of PHP usually checks whether variable is set/declared and it is different/other than the NULL. If the variable is unset using the unset() function in PHP then it is no need to be considered at all to set. The isset() Function will return the value TRUE only if the variable existed which is not NULL. Otherwise isset() function will return the value FALSE value when the function will check the variable which is assigned to the NULL term. NULL character “\0” is not at all equivalent to the PHP NULL constant term. If multiple terms passed to isset() then it will return TRUE value if all the parameters considered.

Explanation:

• $variable: A variable is required which is specified to check
• ……. : It is an optional value/values or variable/variables to check

How does isset() Function works in PHP

The isset() function works by returning the value TRUE if the $variable exists in the isset() function (isset () programming code) which has the value which is other than NULL value. It is FALSE otherwise. The isset() function works from the PHP version 4.0. The return type of the isset() function of PHP programming language is Boolean. If the PHP isset () function are passed with the multiple variables then isset() will TRUE only if all the variables are set. The variable of the isset() function can be unset using the unset() function. Isset () function also works by accepting the multiple variables/many variables etc.. From the PHP 5.4.0 version, non-numeric offsets of strings will return FALSE value/values.

Examples to implement isset() Function in PHP

Example #1

Explanation: In the above isset() program, a variable ‘a” is declared and also defined with the value “10”. Then an isset() function inside the IF condition is made to return the value TRUE or FALSE but here the variable “a” is defined so the output is obviously “TRUE”. If the isset() function will return/print the value “FALSE” if the isset() returns FALSE value.

Example #2

"; > else < echo "The Variable 'a' is now unset.
"; > $b = null; if (isset($b)) < echo "The Variable 'b' is now set.
"; > else < echo "The Variable 'b' is now unset.
"; > if (isset($c)) < echo "The Variable 'c' is now set.
"; > else < echo "The Variable 'c' is now unset.
"; > ?>

Explanation: In the above example, a new variable “a” is created using with the value “10”. It means the value is set for the variable a. So the isset($a) will return TRUE value. If the IF condition of TRUE value then the statements inside the IF condition will be printed. It will print “The variable ‘a’ is now set”. If the IF condition returns FALSE value then the ELSE condition’s statements will be printed. Then variable “b” is created by assigning the NULL value. So the “isset($b)” will return the “FALSE” value. It meanse If(FALSE) will print the statements which are inside the ELSE condition which is “The Variable ‘b’ is now unset” because IF condition is FALSE and gone to the ELSE condition.

Now the isset($c) is placed inside the IF condition but the variable “$c” is not assigned with any value so the value of the “$c” is considered as NULL/FALSE value. So the IF condition’s value becomes FALSE and bypasses the IF condition and goes to the ELSE condition and prints the statements which are in the ELSE condition. It will print “The variable ‘c’ is now unset”.

Example #3

Explanation: In the above example, variable’s “$a1”, “$b1”, “$c1” variables are created with the values “51”, “61” and “NULL”. Here multiple variables are checked whether all the values to the variable’s are assigned or not. Here isset ($a1,$b1,$c1) inside of the IF condition returns the FALSE value because the variable “$c1” value is declared as the value “NULL” so the ELSE condition’s statements will be printed. It will print “Here All or Any variables are now Unset”. You can add as many variables as needed inside isset() function to check whether they are declared/set or undeclared/unset/NULL.

Example #4

 "; echo "==> 1. checking the var11 using isset().
 "; var_dump (isset($var11)); echo "

==> 2. checking the var21 using isset().
 "; var_dump (isset($var21)); > unset ($var11); unset ($var21); echo "
 
The Variables which are after the unset::
 "; var_dump (isset($var11)); var_dump (isset($var21)); ?>

Explanation: In the above example, isset() and unset() functions are used in the PHP programming language. The Variables “$var11” and “var21” are created with the values “test1” and “another test2”. The values can either be a string value or integer value or any other etc. So the isset($var11) and isset($var21) will return the value TRUE. So the IF condition will return TRUE and prints the statements which are present inside the IF condition. Var_dump() is used to check whether the isset($var11) and isset($var21) is TRUE or not. Then again unset() function is used to unset the values of $var11 and $var21 variables. Now again checked the isset($var11) and isset($var21) values using the var_dump() function and it will return the value FALSE “bool(false)”. You can check the output of the above example to understand the unset() concept better using the image in the output section.

Example #5

Explanation: This is the example to check whether the session variable is available or not using the isset() function. Here “$user1” is created and assigned a string value “pavankumarsake”. Then session id is created and assigned the $user1 variable to it. So the isset(session variable) will return TRUE value and the IF condition becomes TRUE and print the statements which are inside the IF condition. If the IF condition returns False then the else statements will be printed. Else statements will be printed only if the $user1 value is not defined/declared or declared with the NULL value.

Conclusion

I hope you understand what is the definition of Isset() Function in PHP and it’s syntax, How isset() function works using PHP along with the various examples to understand the concept of isset() function.

Final thoughts

This is a guide to isset() Function in PHP. Here we discuss Syntax to isset() Function in PHP, how does it work,examples with codes and outputs.

What is the use of ‘isset’ in PHP?, Teams. Q&A for work. Connect and share knowledge within a single location that is structured and easy to search. Learn more

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.

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

View the example in the browser

Practice here online :

How does isset() Function works in PHP, The isset() function works by returning the value TRUE if the $variable exists in the isset() function (isset() programming code) which has the value which is other than NULL value. It is FALSE otherwise. The isset() function works from the PHP version 4.0. Th…

What is the difference between ‘isset()’ and ‘!empty()’ in PHP?

Isset function

ISSET checks the variable to see if it has been set. In other words, it checks to see if the variable is any value except NULL or not assigned a value. ISSET returns TRUE if the variable exists and has a value other than NULL. That means variables assigned a «», 0, «0», or FALSE are set, and therefore are TRUE for ISSET.

Example

"); > $my_array = array(); echo isset($my_array['New_value']) ? 'array is set.' : 'array is not set.'; ?>

Output

This will produce the following output −

0 is set with isset function array is not set.

!empty function

EMPTY checks to see if a variable is empty. Empty is interpreted as: «» (an empty string), 0 (integer), 0.0 (float)`, «0» (string), NULL, FALSE, array() (an empty array), and «$var;» (a variable declared, but without a value in a class.

Example

 echo "nn"; $new_val = 1; if (!empty($new_val)) < echo $new_val . ' is considered set'; >?>

Output

This will produce the following output −

0 is considered empty 1 is considered set

How to use isset() in PHP, It’s called «lazy evaluation». Conditions aren’t checked simultaneously, but one at a time in order from left to right: if any of a series of ANDed criteria is false, then PHP doesn’t bother wasting any time checking the subsequent criteria, because it doesn’t matter what they are, the final result will …

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PHP isset() Function

Check whether a variable is empty. Also check whether the variable is set/declared:

$a = 0;
// True because $a is set
if (isset($a)) echo «Variable ‘a’ is set.
«;
>

$b = null;
// False because $b is NULL
if (isset($b)) echo «Variable ‘b’ is set.»;
>
?>

Definition and Usage

The isset() function checks whether a variable is set, which means that it has to be declared and is not NULL.

This function returns true if the variable exists and is not NULL, otherwise it returns false.

Note: If multiple variables are supplied, then this function will return true only if all of the variables are set.

Tip: A variable can be unset with the unset() function.

Syntax

Parameter Values

Parameter	Description
variable	Required. Specifies the variable to check
.	Optional. Another variable to check

Technical Details

Return Value:	TRUE if variable exists and is not NULL, FALSE otherwise
Return Type:	Boolean
PHP Version:	4.0+
PHP Changelog:	PHP 5.4: Non-numeric offsets of strings now returns FALSE

❮ PHP Variable Handling Reference

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