The isset() function determines whether a variable has been set. A variable with a blank or zero value returns true, because blank and zero are considered values.

result = isset (string);

string Required. A string that contains a variable name.

true Integer. The specified variable has a value.
false Integer. The specified variable does not have a value.
runhost = "beyondtrust1";
result = isset ("runhost");

In this example, result contains an integer value of 1 (true) because the runhost variable has a value of beyondtrust1.

For more information, please see unset.