PHP empty
Summary: in this tutorial, you’ll learn how to use the PHP empty() construct to check if a variable is empty.
Introduction to the PHP empty() construct
The empty() construct accepts a variable and returns true if the variable is empty. Otherwise, it returns false.
empty(mixed $v): boolCode language: PHP (php)
A variable is empty when if it does not exist or if its value is equal to false. In other words, a variable that is not set is empty or its value equals the following:
The false
The integer 0
The float 0.0 and -0.0
The string "0"
The empty string ''
An array with no element
null
SimpleXML objects created from empty elements that have no attributes.Code language: PHP (php)
The empty($v) is essentially the same as the following expression that uses the isset() and equality (==) operator:
!isset($v) || $v == falseCode language: PHP (php)
Like the isset() construct, the empty() is a language construct, not a function. Therefore, you cannot call it using variable functions.
However, you can work around it by defining a function that uses the empty() construct and call that function using variable functions:
function not_exist_or_false($var) : bool
{
return empty($var);
}
Code language: HTML, XML (xml)
Alternatively, you can use the arrow function syntax to define a new function that uses the empty() construct:
$empty = fn($var) => empty($var);
Code language: HTML, XML (xml)
PHP empty() examples
The following example returns true because the $count variable is not declared:
var_dump(empty($count));
Code language: PHP (php)
Output:
bool(true)Code language: PHP (php)
The following example also returns true because $count is zero, which is considered false:
$count = 0;
var_dump(empty($count));
Code language: PHP (php)
Output:
bool(true)Code language: PHP (php)
If a variable’s value is false, then the empty() returns true. The following returns true for all the falsy values in the $falsy_values array:
$falsy_values = [false, 0, 0.0, "0", '', null, []];
foreach($falsy_values as $value) {
var_dump(empty($value));
}
Code language: PHP (php)
When to use the PHP empty() construct
In practice, you use the empty() construct in the situation that you’re not sure if a variable even exists.
For example, suppose you receive an array $data from an external source, e.g., an API call or a database query.
To check if the $data array has an element with the key 'username' and it is not empty, and you may use the following expression:
isset($data['username']) && $data['username'] !== '')Code language: PHP (php)
However, it’s shorter you use the empty() construct:
!empty($data['username'])Code language: PHP (php)
Summary
- Use the PHP
empty()construct to check if a variable is not set or its value isfalse.