Is null a type in php?

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, and REMOVED as of PHP 8.0.0. 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.

quickpick ¶

11 years ago

Note: empty array is converted to null by non-strict equal '==' comparison. Use is_null[] or '===' if there is possible of getting empty array.

$a = array[];

$a == null  $person['cell'] ];
}

print_r[$friends];

Array
[
    [0] => Array
        [
            [Name] =>
            [Phone] =>
        ]

    [1] => Array
        [
            [Name] =>
            [Phone] =>
        ]

]

This means that:
* NULL == NULL['foo']['bar']['whatever']

This can be slightly confusing if you accidentally slip a NULL into an array of other items.

Hayley Watson ¶

4 years ago

NULL is supposed to indicate the absence of a value, rather than being thought of as a value itself. It's the empty slot, it's the missing information, it's the unanswered question. It's not a jumped-up zero or empty set.

This is why a variable containing a NULL is considered to be unset: it doesn't have a value. Setting a variable to NULL is telling it to forget its value without providing a replacement value to remember instead. The variable remains so that you can give it a proper value to remember later; this is especially important when the variable is an array element or object property.

It's a bit of semantic awkwardness to speak of a "null value", but if a variable can exist without having a value, the language and implementation have to have something to represent that situation. Because someone will ask. If only to see if the slot has been filled.

Anonymous ¶

4 years ago

Note: Non Strict Comparison '==' returns bool[true] for

null == 0