isset() will return FALSE if testing a variable that has been set to NULL. Like the name implies, it is designed to verify if a variable given to it is set, returning a boolean value based on the result. We use the isset function to check if any variable that is passed, exists in the code and also possess some value. The isset() function checks whether a variable is set, which means that it has to be declared and is not NULL. The isset() function is a built-in function of PHP, which is used to determine that a variable is set or not. When we use ternary operator: We use the ternary operator when we need to simplify the if-else statements that are simply assigning values to variables depending on a condition. isset() Function The isset() function is an inbuilt function in PHP which checks whether a variable is set and is not NULL. That’s called a ternary operator and it’s mainly used in place of an if-else statement. If you aren't experienced with using ternary operators, write your code using if/else first, then translate the code into ? It is FALSE otherwise. PHP logical && operator . PHP's behaviour when using more than one ternary operator within a single statement is non-obvious." 's and :'s. Evaluation goes from left to right and stops as soon as an unset variable is encountered. This function also checks if a declared variable, array or array key has null value, if it does, isset() returns false, it returns true in all other possible cases. Comparison. Also note that a NULL byte ("\0") is not equivalent to the PHP NULL constant. PHP isset() function. PHP isset() function is used to check if a variable has been set or not. This can be useful to check the submit button is clicked or not. An advantage of using a ternary operator is that it reduces the huge if-else block to a single line, improving the code readability and simplify it. In the example you gave it can be used to retrieve a value from an array given isset returns true In PHP 7, a new feature, null coalescing operator (??) The differences between these functions will be shown here. It means we check the value of any particular variable. If the PHP isset() function are passed with the multiple variables then isset() will TRUE only if all the variables are set. The isset() function works from the PHP version 4.0. However, it has some quirks and behaviours that are very much worth knowing as they can easily catch out even experienced developers. In case-1 of the picture, both of the taps are closed, so the water is not flowing down. This function returns true … The Null coalescing operator returns its first operand if it exists and is not NULL; otherwise it returns its second operand. This above pictorial helps you to understand the concept of LOGICAL AND operation with an analogy of taps and water. The return type of the isset() function of PHP programming language is Boolean. Which explains that if both of conditions are FALSE or 0, the return is FALSE or 0. Definition and Usage. The isset() function returns true if variable is set and not null. The isset() function will return true or false value. PHP isset() PHP isset() function is used to check if a variable exists in the code or not. If multiple parameters are supplied then isset() will return TRUE only if all of the parameters are set. If a variable is considered set, means the variable is declared and has a different value from the NULL. PHP isset() function. isset() and empty() are often viewed as functions that are opposite, however this is not always true. In short, it checks that the variable is declared and not null. PHP isset() function syntax. It is used to replace the ternary operation in conjunction with isset() function. Output: Adult. isset() From PHP manual – isset(): isset — Determine if … has been introduced. isset() is one of the most important tools at your disposal to validate data in PHP. '-' (Null Coalesce Operator).