(PHP 4, PHP 5, PHP 7)
empty — Determine whether a variable is empty
empty ( mixed $var ) : bool
Determine whether a variable is considered to be empty. A variable is considered empty if it does not exist or if its value equals false. empty() does not generate a warning if the variable does not exist.
var
Variable to be checked
Note:
Prior to PHP 5.5, empty() only supports variables; anything else will result in a parse error. In other words, the following will not work: empty(trim($name)). Instead, use trim($name) == false.
No warning is generated if the variable does not exist. That means empty() is essentially the concise equivalent to !isset($var) || $var == false.
Returns false if var exists and has a non-empty, non-zero value, aka falsey, see conversion to boolean. Otherwise returns true.
Example #1 A simple empty() / isset() comparison.
<?php
$var = 0;
// Evaluates to true because $var is empty
if (empty($var)) {
echo '$var is either 0, empty, or not set at all';
}
// Evaluates as true because $var is set
if (isset($var)) {
echo '$var is set even though it is empty';
}
?> Example #2 empty() on String Offsets
PHP 5.4 changes how empty() behaves when passed string offsets.
<?php $expected_array_got_string = 'somestring'; var_dump(empty($expected_array_got_string['some_key'])); var_dump(empty($expected_array_got_string[0])); var_dump(empty($expected_array_got_string['0'])); var_dump(empty($expected_array_got_string[0.5])); var_dump(empty($expected_array_got_string['0.5'])); var_dump(empty($expected_array_got_string['0 Mostel'])); ?>
Output of the above example in PHP 5.3:
bool(false) bool(false) bool(false) bool(false) bool(false) bool(false)
Output of the above example in PHP 5.4:
bool(true) bool(false) bool(false) bool(false) bool(true) bool(true)
Note: Because this is a language construct and not a function, it cannot be called using variable functions.
Note:
When using empty() on inaccessible object properties, the __isset() overloading method will be called, if declared.
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https://www.php.net/manual/en/function.empty.php