What is the difference between isset and empty in PHP?

The isset function and the empty function are both used to determine if a variable exists or is empty, but there are some differences between the two.

1. isset function:

1. The isset function is used to check if a variable exists and is not null. It returns true if the variable exists and is not null, otherwise it returns false.
2. The isset function can accept multiple arguments at once, and will return false if any of them are missing or null.

1. empty function:

1. The empty function is used to check if a variable is empty. It returns true if the variable is one of the following conditions, otherwise it returns false:
   – The variable is 0 or the string “0”;
   – The variable is an empty string (“”);
   – The variable is false;
   – The variable is an empty array (array());
   – The variable is null;
   – The variable is undefined.

In conclusion:

1. The isset function checks if a variable exists and is not null.
2. The empty function is used to determine if a variable is empty.
3. The isset function can check multiple variables, while the empty function can only check one variable.
4. The empty function will return true for both 0 and the string “0”, while the isset function will return false.