Using PHP count() and sizeof() Functions to Count Array Elements and Object Properties

PHP provides the count() function (alias sizeof() ) to obtain the number of elements in an array or the number of properties in an object.

Syntax:

<code>count ( mixed $array , int $mode )</code>

Parameters:

$array : an array or a Countable object.

$mode (optional): set to COUNT_RECURSIVE (or 1 ) to count recursively.

Return value: the number of elements. If the argument is neither an array nor a Countable object, the function returns 1 ; if $array is null , it returns 0 .

Usage examples:

1. Counting array elements:

<code>&lt;?php
$a[0] = 1;
$a[1] = 3;
$a[2] = 5;
var_dump(count($a));
var_dump(count(null));
var_dump(count(false));
?&gt;</code>

Output (PHP 7.2+):

<code>int(3)
int(0)
int(1)</code>

2. Counting object properties via the Countable interface:

<code>&lt;?php
class C implements Countable {
    public function count() {
        return 0;
    }
}
$a = [];
var_dump($a);
echo 'array is empty: ';
var_dump(empty($a));
echo "<br>";
$c = new C;
var_dump($c);
echo "<br>";
echo 'Countable is empty: ';
var_dump(empty($c));
echo "<br>";
?&gt;</code>

Output shows the array is empty (bool true) while the Countable object is not considered empty (bool false).