Isset :
1. isset checks to see if the variable have any value except NULL or not assigned a value.
2. isset returns true, if that varibale exists and have value other than NULL.
3. If variable assigned a value like " ", 0, "0" or FALSE are set. So, isset returns true.
Empty :
1. EMPTY checks to see if a variable is empty.
2. Empty is interpreted as : " " (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), and "$var;" (a variable declared, but without a value in a class.
Some Examples :
1. $nullVar = NULL;
if ( isset($nullVar)) -- This would be FALSE
if ( empty($nullVar)) -- This is TRUE
2. $singleQuoteVar = '';
$dblQuoteVar = "";
if ( isset($singlequoteVar)) -- This would be TRUE
if ( empty($singlequoteVar)) -- This is TRUE
if ( isset($dblquoteVar)) -- This would be TRUE
if ( empty($dblquoteVar)) -- This is TRUE
3. $zeroValue = 0;
if ( isset($zeroValue)) -- This would be TRUE
if ( empty($zeroValue)) -- This is TRUE
4. $TrueBoolValue = TRUE == 1;
$FalseBoolValue = FALSE == 0;
if ( isset($TrueBoolValue)) -- This would be TRUE
if ( empty($TrueBoolValue)) -- This is FALSE
if ( isset($FalseBoolValue)) -- This would be TRUE
if ( empty($FalseBoolValue)) -- This is TRUE
5. $arrVar = array():
if ( isset($arrVar)) -- This would be TRUE
if ( empty($arrVar)) -- This is TRUE
