For arrays and strings, PHP follows the convention that 'empty' means 'has no members' although arrays and strings are not technically sets.

You can see the ambiguity I'm talking about with the isset() function. In the PHP world, apparantly uninitialized variables have the Null value, and isset on such a variable returns FALSE. PHP shows that $a exists, and has a NULL value. Tip: The isset() function returns true if the variables (which are sent to the function in parameters) are set and not null. Introduction to the PHP null coalescing operator. The Null coalescing operator returns its first operand if it exists and is not NULL otherwise it returns its second operand. How are we supposed to reliably check for the existence of a variable in PHP?Įdit: there is clearly a difference in PHP between variables that are not set, and variables that are set to NULL: NULL) 1 respuesta Ordenado por: 6 PHP tiene básicamente tres funciones para el manejo de nulos, vacíos, en blanco, no declarados. Summary: in this tutorial, you’ll learn about the PHP Null coalescing operator to assign a value to a variable if the variable doesn’t exist or null. Given that, what's the best way to actually check for the existence of a variable? I tried something like: if(isset($v) || is necessary to avoid the warning when $v is not set) but is_null() has a similar problem to isset(): it returns TRUE on unset variables! It also appears that: = NULL) From the isset() docs: isset() will return FALSE if testing a variable that has been set to NULL.īasically, isset() doesn't check for whether the variable is set at all, but whether it's set to anything but NULL.

Php isset null