PHP检查数组是否为空逻辑不起作用

Question

I have a page that loads and creates an empty array:

$_SESSION['selectedItemIDs'] = array();

If the user hasn't added any selections that get stored in the array I then check the array and branch accordingly, but there appears to be some error in my logic/syntax that is failing here.

Here's where I test if the $_SESSION['selectedItemIDs'] is set but empty:

if (isset($_SESSION['selectedItemIDs']) && $_SESSION['selectedItemIDs'] !== '') {
    // update the selections in a database
} else {
    // nothing selection so just record this in a variable
$selectedItems = 'no selected items were made';
}

When testing this with no selections if I print the $_SESSION['selectedItemIDs'] array I get this:

[selectedItemIDs] => Array
    (
    )

however the $selectedItems variable is not being set - it's evaluating the if test as true when I would expect it to be false, but I'm obviously misunderstanding something here.

Answer 1

Use empty() function.

empty() - it will return true if the variable is an empty string, false, array(), NULL, “0?, 0, and an unset variable.

Syntax

empty(var_name)

Return value

FALSE if var_name has a non-empty and non-zero value.

Value Type :

Boolean

List of empty things :

• "0" (0 as a string)
• 0 (0 as an integer)
• "" (an empty string)
• NULL
• FALSE
• "" (an empty string)
• array() (an empty array)
• $var_name; (a variable declared but without a value in a class)

Code

if (!empty($_SESSION['selectedItemIDs']) ) {
    // update the selections in a database
} else {
    // nothing selection so just record this in a variable
$selectedItems = 'no selected items were made';
}

Answer 2

$_SESSION['selectedItemIDs'] = array();

this variable is already set, but is empty. isset($_SESSION['selectedItemIDs']) check if variable exists, even if it's nothing in.

To check if there is anything just use

empty($_SESSION['selectedItemIDs']);

PHP DOC - empty

Answer 3

if (!empty($_SESSION['selectedItemIDs'])) {
    // update the selections in a database
} else {
    // nothing selection so just record this in a variable
    $selectedItems = 'no selected items were made';
}

isset($_SESSION['selectedItemIDs']) => it will check is this parameter is set or not which is correct.

$_SESSION['selectedItemIDs'] !== '' => this will exactly compare that your parameter type is not '' but here i guess your selectedItemIDs is array so it let you go inside

Answer 4

You can check the count of this array.

if (isset($_SESSION['selectedItemIDs']) && count($_SESSION['selectedItemIDs']) > 0) {
    // update the selections in a database
} else {
    // nothing selection so just record this in a variable
$selectedItems = 'no selected items were made';
}