About Lesson
isset() and empty()
These two functions are important when working with forms, variables, and conditions.
1. isset()
isset() checks if a variable is set and not NULL.
PHP
<?php
$name = "John";
if (isset($name)) {
echo "The variable 'name' is set.";
} else {
echo "The variable 'name' is not set.";
}
?>Output: The variable ‘name’ is set.
If we don’t declare $name, then isset($name) will return false.
2. empty()
empty() checks if a variable is empty. A variable is considered empty if it is:
""(empty string)0(integer zero)0.0(float zero)"0"(string zero)NULLfalse- An empty array
[]
PHP
<?php
$age = 0;
if (empty($age)) {
echo "The variable 'age' is empty.";
} else {
echo "The variable 'age' has a value.";
}
?>Output: The variable ‘age’ is empty.
If we don’t declare $name, then isset($name) will return false.
3. isset() vs empty() Difference
| Function | Returns TRUE when… |
|---|---|
isset() | Variable exists and is NOT NULL |
empty() | Variable is empty ( “”, 0, “0”, NULL, false, [] ) |
4. Practical Example with Form:
PHP
<!DOCTYPE html>
<html>
<head>
<title>isset() and empty() Example</title>
</head>
<body>
<form method="post" action="">
Name: <input type="text" name="name">
<input type="submit" name="submit" value="Submit">
</form>
<?php
if (isset($_POST['submit'])) { // Check if form is submitted
$name = $_POST['name'];
if (empty($name)) {
echo "<p style='color:red;'>Name cannot be empty!</p>";
} else {
echo "<p style='color:green;'>Hello, " . $name . "!</p>";
}
}
?>
</body>
</html>Explanation:
isset($_POST['submit'])→ checks if the Submit button was clicked.empty($name)→ checks if the input box is empty.