{"id":2578,"date":"2021-09-06T03:02:03","date_gmt":"2021-09-06T03:02:03","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=2578"},"modified":"2025-04-06T05:17:20","modified_gmt":"2025-04-06T05:17:20","slug":"php-is_null","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-tutorial\/php-is_null\/","title":{"rendered":"PHP is_null"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the PHP is_null()<\/code> construct to check if a variable is null<\/code>.<\/p>\n\n\n\n

Introduction to the PHP is_null() construct #<\/a><\/h2>\n\n\n\n

PHP is_null()<\/code> accepts a variable<\/a> and returns true<\/code> if that variable is null<\/a><\/code>. Otherwise, it returns false<\/code>.<\/p>\n\n\n

is_null(mixed $v): bool<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, the $v<\/code> is the variable to check. If $v<\/code> doesn’t exist, the is_null()<\/code> also returns true<\/code> and issues a notice.<\/p>\n\n\n\n
<?php<\/span>\n\n$f = is_null;<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
However, you can define a function that wraps the is_null()<\/code> construct like this:<\/p>\n\n\n
<?php<\/span>\n\nfunction<\/span> isnull<\/span>($v)<\/span>: bool<\/span>\n<\/span>{\n    return<\/span> is_null($v);\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
<?php<\/span>\n\n$isnull = fn($v) => is_null($v);\n\n$color = null<\/span>;\necho<\/span> $isnull($color); \/\/ true<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
PHP is_null() examples #<\/a><\/h2>\n\n\n\n
The following example uses the is_null()<\/code> construct and returns true<\/code> because the $count<\/code> variable doesn’t exist:<\/p>\n\n\n
<?php<\/span>\n\nvar_dump(is_null($count));<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
This code also issues a notice:<\/p>\n\n\n
Notice: Undefined variable: $count<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example uses the is_null()<\/code> and returns true<\/code> because the $count<\/code> variable is null<\/code>:<\/p>\n\n\n
<?php<\/span>\n\n$count = null<\/span>;\nvar_dump(is_null($count)); \/\/ true<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example uses the is_null()<\/code> and returns false because the $count<\/code> variable is not null<\/code>:<\/p>\n\n\n
<?php<\/span>\n\n$count = 1<\/span>;\nvar_dump(is_null($count)); \/\/ false<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
PHP is_null() with array #<\/a><\/h2>\n\n\n\n
The following example uses the is_null()<\/code> to check if the element with the key link<\/code> is null<\/code> or not. It returns true<\/code> because the element doesn’t exist:<\/p>\n\n\n
<?php<\/span>\n\n$colors = [\n    'text'<\/span> => 'black'<\/span>,\n    'background'<\/span> => 'white'<\/span>\n];\n\nvar_dump(is_null($colors['link'<\/span>]));<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
It also returns a notice:<\/p>\n\n\n
Notice: Undefined index: link<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
PHP is_null() with string index #<\/a><\/h2>\n\n\n\n
The following example uses the is_null()<\/code> to check if the element at index 5 in the string $message<\/code> is null or not:<\/p>\n\n\n
<?php<\/span>\n\n$message = 'Hello'<\/span>;\n\nvar_dump(is_null($message[5<\/span>]));<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
It returns false and issues a notice:<\/p>\n\n\n
PHP Notice:  Uninitialized string offset: 5<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
PHP is_null(), equal operator (==), and identity operator (===) #<\/a><\/h2>\n\n\n\n
The echo displays an empty string for the false value, which is not intuitive. The following defines a function that displays false as the string false instead of an empty string:<\/p>\n\n\n
<?php<\/span>\n\nfunction<\/span> echo_bool<\/span>(string $title, bool $v)<\/span>: void<\/span>\n<\/span>{\n    echo<\/span> $title, \"\\t\"<\/span>, $v === true<\/span> ? 'true'<\/span> : 'false'<\/span>, PHP_EOL;\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Comparing falsy values with null using equal operator (==) #<\/a><\/h3>\n\n\n\n
Comparing a falsy value with null<\/code> using the equal operator (==<\/code>) will return true<\/code>. For example:<\/p>\n\n\n\n
The following example compares null<\/code> with falsy values using the equal operator (==<\/code>):<\/p>\n\n\n
<?php<\/span>\n\nfunction<\/span> echo_bool<\/span>(string $title, bool $v)<\/span>: void<\/span>\n<\/span>{\n    echo<\/span> $title, \"\\t\"<\/span>, $v === true<\/span> ? 'true'<\/span> : 'false'<\/span>, PHP_EOL;\n}\n\necho_bool('null == false:'<\/span>, null<\/span> == false<\/span>);\necho_bool('null == 0:'<\/span>, null<\/span> == 0<\/span>);\necho_bool('null == 0.0:'<\/span>, null<\/span> == 0.0<\/span>);\necho_bool('null ==\"0\":'<\/span>, null<\/span> == false<\/span>);\necho_bool('null == \"\":'<\/span>, null<\/span> == ''<\/span>);\necho_bool('null == []:'<\/span>, null<\/span> == []);\necho_bool('null == null:'<\/span>, null<\/span> == null<\/span>);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
null == false:  true\nnull == 0:      true\nnull == 0.0:    true\nnull ==\"0\":     true\nnull == \"\":     true\nnull == []:     true\nnull == null:   true<\/code><\/span>Code language:<\/span> plaintext<\/span> (<\/span>plaintext<\/span>)<\/span><\/small><\/pre>\n\n\n
Comparing falsy value with null using identity operator (===) #<\/a><\/h3>\n\n\n\n
The following example uses the identity operator (===<\/code>) to compare null with falsy values, only null === null<\/code> returns true<\/code>.<\/p>\n\n\n
<?php\n\nfunction echo_bool(string $title, bool $v): void\n{\n    echo $title, \"\\t\", $v === true ? 'true' : 'false', PHP_EOL;\n}\n\necho_bool('null === false:', null === false);\necho_bool('null === 0:', null === 0);\necho_bool('null === 0.0:', null === 0.0);\necho_bool('null ===\"0\":', null === false);\necho_bool('null === \"\":', null === '');\necho_bool('null === []:', null === []);\necho_bool('null === null:', null === null);<\/code><\/span>Code language:<\/span> plaintext<\/span> (<\/span>plaintext<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
null<\/span> === false<\/span>: false<\/span>\nnull<\/span> === 0<\/span>:     false<\/span>\nnull<\/span> === 0.0<\/span>:   false<\/span>\nnull<\/span> ===\"0\"<\/span>:    false<\/span>\nnull<\/span> === \"\"<\/span>:    false<\/span>\nnull<\/span> === []:    false<\/span>\nnull<\/span> === null<\/span>:  true<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Comparing falsy values with null using the PHP is_null() #<\/a><\/h3>\n\n\n\n
The following example uses the is_null()<\/code> to check if falsy values are null<\/code>:<\/p>\n\n\n
<?php<\/span>\n\nfunction<\/span> echo_bool<\/span>(string $title, bool $v)<\/span>: void<\/span>\n<\/span>{\n    echo<\/span> $title, \"\\t\"<\/span>, $v === true<\/span> ? 'true'<\/span> : 'false'<\/span>, PHP_EOL;\n}\n\necho_bool('is_null(false):'<\/span>, is_null(false<\/span>));\necho_bool('is_null(0):'<\/span>, is_null(0<\/span>));\necho_bool('is_null(0.0)'<\/span>, is_null(0.0<\/span>));\necho_bool('is_null(\"0\"):'<\/span>, is_null(\"0\"<\/span>));\necho_bool('is_null(\"\"):'<\/span>, is_null(\"\"<\/span>));\necho_bool('is_null([]):'<\/span>, is_null([]));\necho_bool('is_null(null):'<\/span>, is_null(null<\/span>));<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
is_null(false<\/span>): false<\/span>\nis_null(0<\/span>):     false<\/span>\nis_null(0.0<\/span>)    false<\/span>\nis_null(\"0\"<\/span>):   false<\/span>\nis_null(\"\"<\/span>):    false<\/span>\nis_null([]):    false<\/span>\nis_null(null<\/span>):  true<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The is_null()<\/code> and identity operator (===<\/code>) return the same result.<\/p>\n\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
    \n
  • The is_null()<\/code> checks a value and returns true<\/code> if that value is null<\/code>. Otherwise, it returns false<\/code>.<\/li>\n\n\n\n
  • The is_null()<\/code> behaves the same as the identity operator (===<\/code>).<\/li>\n<\/ul>\n
    \n\t
    \n\t\t
    Did you find this tutorial useful?<\/div>\n\t\t
    \n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t
    \n\t\t
    \n\t\t\t
    <\/div>\n\t\t\t\n\t\t\t
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Alternatively, you can define an arrow function<\/a>, assign it to a variable, and use that variable function.<\/p>\n\n\n
Since the is_null()<\/code> is a language construct, not a function<\/a>, you cannot call it via variable functions<\/a>. For example, the following statement will result in an error:<\/p>\n\n\n