The empty () function and the isset () function in PHP

In the development process, often encountered in the judgment of the existence of variables and whether it is empty, especially the array, if the access to a non-existent element of the array, there will be a notice level of error burst, but also a logic is not rigorous performance.

First, look at the empty () function:

Determines whether a function is empty. So what is the case in PHP that is considered empty? The first is that the variable does not exist , and the second is that the value of this variable is equal to FALSE. That is, empty ($var) is equivalent to!isset ($var) | | $var = = FALSE.

Then look at the Isset () function:

Determine if a variable exists and his value is not equal to null.

If the unset ($var), the $var will not exist;

If a variable is given NULL, the function also returns FALSE;

And this function can have more than one parameter, which returns TRUE only if all arguments are present and the value is not equal to NULL.

Because NULL is also a value equivalent to a value of false, the emtpy () function equals isset () plus a value that determines whether the variable is equal to the other equivalent of false.