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.

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


isset(variable, ....);

eg. $x = $_POST[‘fisrt_name’];

Parameter Values

Variable Required. Specifies the variable to check
... Optional. Another variable to check

<!DOCTYPE html>
$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."; } ?> </body> </html>

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