PHP sizeof: How to Count Elements in Arrays with Examples

The sizeof function in PHP exists to help developers know how many items an array holds.

Understand the sizeof Function in PHP

The sizeof in PHP returns the number of elements in an array.

Here is the syntax:

sizeof(array, mode);

• array: The input array to measure.
• mode: Optional. You can use COUNT_RECURSIVE to include elements in subarrays.

It returns an integer that matches the count of elements. If the array is empty, it returns 0.

Here is a quick example:

$items = ["pen", "book", "table"];
echo sizeof($items);

This example outputs 3 because the array holds three items. PHP counts each main element only. It does not check inside other arrays unless you set recursive mode.

The sizeof helps when code logic depends on the array size. You can use it to limit loops or control how many times a process runs. It also acts as a fast way to check if array indexes exist before using them.

Use the sizeof Function in Arrays

Indexed arrays use numeric keys:

$fruits = ["apple", "mango", "banana"];
echo sizeof($fruits);

This returns 3 because the array has three values linked to keys 0, 1, and 2.

Associative arrays use named keys:

$user = ["name" => "Ali", "age" => 25];
echo sizeof($user);

It returns 2 because two key-value pairs exist in the array.

Multidimensional arrays hold arrays inside them:

$data = [
  ["red", "green"],
  ["blue", "yellow"]
];
echo sizeof($data);

This returns 2 because it counts only the top-level elements unless COUNT_RECURSIVE is set.

The sizeof works with objects that implement Countable:

class MyData implements Countable {
    public function count() {
        return 5;
    }
}
$obj = new MyData();
echo sizeof($obj);

This returns 5 because the object’s count() method sets that value.

If the variable is null or an empty array, sizeof returns 0. This stops errors when you count

So, how to handle null or empty arrays with sizeof?

Before PHP 8:

• If you used sizeof() on something that is not an array or countable object, it returned 1.
• If it was NULL, it returned 0.

From PHP 8 onward:

• Using sizeof() on anything that is not an array or a countable object will give an error instead of returning 1.
• So using it on a number, string, or normal object now causes a TypeError.

The Differences Between sizeof and count

The sizeof is an alias of count. Both behave the same way in normal use. Developers often choose one based on style or readability.

Here is a table that shows you the key differences:

You can use either function. However, count is more common in most PHP code.

Examples of sizeof Function in PHP

Count the Indexed Array Items:

$colors = ["red", "blue", "green", "yellow"];
echo sizeof($colors);

This returns 4 because there are four elements in the array. It counts only top-level values and does not check inside subarrays.

Recursive Count for Multidimensional Array:

$data = [
    ["pen", "pencil"],
    ["book", "paper"]
];
echo sizeof($data, COUNT_RECURSIVE);

This returns 6 because it counts each subarray item along with the top-level arrays.

Count Items in an Object:

class Box implements Countable {
    public function count() {
        return 8;
    }
}
$box = new Box();
echo sizeof($box);

This returns 8 because the count() method defines the value returned by sizeof.

Handle Null Variable:

$var = null;
echo sizeof($var);

This will show you an error. Here is the output:

Uncaught TypeError: sizeof(): Argument #1 ($value) must be of type Countable|array, null given in /index.php

Wrapping Up

In this article, you learned how sizeof works in PHP and how it can count elements in arrays and objects.

Here is a quick recap:

• sizeof returns the number of elements in an array or Countable object.
• It is an alias of count and both work the same way.
• Use it to check the array size before running loops or other logic.
• It works with indexed, associative, and multidimensional arrays.

FAQs

$array = array("apple", "banana", "orange");
$count = sizeof($array);
echo $count; // Output: 3

$array = array("red", "green", "blue");
echo sizeof($array); // 3
echo count($array);  // 3

$array = array(
    "fruits" => array("apple", "banana"),
    "colors" => array("red", "blue")
);
echo sizeof($array); // 2
echo sizeof($array, COUNT_RECURSIVE); // 6

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