What is empty() Function in PHP? (With Examples)

The empty() function in PHP is used to check whether a variable is considered empty. It is commonly used in PHP scripts to validate form fields, check variable values, and handle optional parameters.

If the variable is empty, empty() returns true; otherwise, it returns false.

Syntax of empty() Function

empty(mixed $var): bool

• $var: The variable you want to check.
• Return Value: Returns true if the variable is empty; otherwise, returns false.

When is a Variable Considered Empty in PHP?

In PHP, a variable is considered empty if it:

• Does not exist.
• Is set to "" (an empty string).
• Is set to 0 (0 as an integer).
• Is set to "0" (0 as a string).
• Is set to NULL.
• Is set to FALSE.
• Is an empty array ([]).
• Is an empty object that implements Countable with count 0.

Basic Example of empty() in PHP

<?php
$name = "";

if (empty($name)) {
    echo "The name field is empty.";
} else {
    echo "The name field is not empty.";
}
?>

Output:

The name field is empty.

In this example, $name is an empty string, so empty($name) returns true.

More Examples of empty() Usage

Example 1: Check If a Form Field is Filled

<?php
$email = $_POST['email'] ?? '';

if (empty($email)) {
    echo "Please enter your email address.";
} else {
    echo "Thank you for providing your email.";
}
?>

Example 2: Using empty() with Numbers

<?php
$quantity = 0;

if (empty($quantity)) {
    echo "Quantity is not set or is zero.";
} else {
    echo "Quantity is available.";
}
?>

Since $quantity is 0, which is considered empty, the output will be:

Quantity is not set or is zero.

Important Points About empty() in PHP

• No Warning for Undefined Variables: Unlike isset(), the empty() function does not throw a warning if the variable is not defined.
• Comparison with isset():
  • isset() checks if a variable is set and not NULL.
  • empty() checks if a variable is considered empty.

Difference Between isset() and empty()

<?php
// Suppose $var is not set at all

var_dump(isset($var)); // Output: bool(false)
var_dump(empty($var)); // Output: bool(true)
?>