count() vs sizeof(): Which PHP Function Should You Use?

Hello PHP developers! Today we discuss the two seemingly simple but often confusing functions count() and sizeof(). Although they can be used interchangeably in most cases, subtle differences are worth knowing.

Understanding the Basics

At first glance count() and sizeof() appear to be completely different functions. count() is a built‑in function, while sizeof() is a language construct. In reality they are aliases in PHP, meaning they are functionally identical and can be used interchangeably to obtain the number of elements in an array or the properties of an object.

Here is an example:

$fruits = ["apple", "orange", "banana"];
$count = count($fruits);
$size = sizeof($fruits);
// Both $count and $size now hold the value 3

In this case both $count and $size contain the value 3.

So, Which One Should You Choose?

Since count() and sizeof() are aliases with identical functionality, the choice mainly depends on personal preference.

Some developers prefer count() because it is more common and appears in other languages. Others favor sizeof() for its brevity and ability to work with any data type.

Tips and Tricks

Now let’s look at some tips and tricks for count() and sizeof():

1. About Speed

If you are a performance enthusiast, know that count() and sizeof() execute at the same speed behind the scenes, so choosing one will not yield a noticeable performance gain.

2. Counting Recursive Elements

Here’s a handy trick: when the COUNT_RECURSIVE flag is set, both count() and sizeof() can count elements recursively, which is especially useful for multidimensional arrays.

$multiArray = [
    "fruits" => ["apple", "orange", "banana"],
    "vegetables" => ["carrot", "lettuce", "tomato"]
];
$countRecursive = count($multiArray, COUNT_RECURSIVE);
// $countRecursive now contains the value 8

3. Counting Objects

Both functions seamlessly handle object properties. So if you are working with objects in PHP, you can rely on either count() or sizeof() to serve you well.

Choosing between count() and sizeof() is like picking an ice‑cream flavor—it depends on your personal taste and coding style. count() is more widely used and aligns with similar functions in other languages, while sizeof() is more concise and can be applied to any data type.