NULL

The special NULL value represents a variable with no value. NULL is the only possible value of type null.

A variable is considered to be null if:

• it has been assigned the constant NULL.

• it has not been set to any value yet.

• it has been unset().

Syntax

There is only one value of type null, and that is the case-insensitive constant NULL.

See also the functions is_null() and unset().

Casting to NULL

Warning

This feature has been DEPRECATED as of PHP 7.2.0. Relying on this feature is highly discouraged.

Casting a variable to null using (unset) $var will not remove the variable or unset its value. It will only return a NULL value.

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https://secure.php.net/manual/en/language.types.null.php