isset() function in php

Question

Hi I want to know what is the use of isset() function in PHP ? Please tell me anyone use of the isset() function in PHP with an example ? Thanks

Satyapriya Nayak · Answer

Hi Vineet 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. Refer http://www.java-samples.com/showtutorial.php?tutorialid=891 Thanks

Senthilkumar · Answer

Hi Vineet iiset() Determines if a variable is set and is not NULL. If a variable has been unset with unset() it will no longer be set. isset() will return FALSE if testing a variable that has been set to NULL. Also note that a NULL byte (\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 set. Evaluation goes from left to right and stops as soon as an unset variable is encountered. There are plenty of example.please go here: http://php.net/manual/en/function.isset.php http://www.toknowmore.net/e/1/php/php-isset-function.php http://itslennysfault.com/php-isset-vs-empty http://snipplr.com/view/11093/