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PHP empty() Function

Quick summary: The PHP empty() construct checks whether a variable is empty.

PHP empty() Syntax 

empty(mixed $value): bool
PHP

PHP empty() Basic examples 

var_dump(empty(0));
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Output:
bool(true)

Zero is considered empty.

var_dump(empty(""));
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Output:
bool(true)

An empty string is considered empty.

PHP empty() Real-world usage 

$input = '';
if (empty($input)) {
    echo 'No input';
}
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Output:
No input

Validates required user input.

PHP empty() Edge cases 

var_dump(empty('0'));
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Output:
bool(true)

The string \"0\" is also considered empty.

PHP empty() Common mistakes

Using empty for strict validation

empty treats many values as false.

Incorrect
empty('0');
Correct
isset($v) && $v !== '';

Use explicit checks when value precision matters.

PHP empty() Frequently Asked Questions

What does empty() do in PHP?

empty() checks whether a variable is empty and returns true or false.

What values are considered empty in PHP?

Values like 0, 0.0, "", "0", null, false, and empty arrays are considered empty.

Does empty() throw a warning for undefined variables?

No, empty() does not generate warnings for undefined variables.

What is the return type of empty()?

empty() returns a boolean value.

Can empty() be used on arrays?

Yes, it returns true if the array has no elements.

Is empty() the same as isset()?

No, isset() checks if a variable is set and not null, while empty() checks for empty values.

Does empty() modify the variable?

No, it only checks the value.

Can empty() be used on object properties?

Yes, but behavior depends on property accessibility.

What is a common use case for empty()?

Validating user input or checking optional values.

Is empty() faster than strlen()?

Yes, empty() is generally faster for checking emptiness.

Does empty("0") return true?

Yes, the string "0" is considered empty.

What is the best practice when using empty()?

Use it carefully when distinguishing between "0" and truly empty values.

PHP empty() Related PHP Functions