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Hàm sizeof() trong PHP

Hướng dẫn cách sử dụng hàm sizeof() về mảng trong lập trình PHP

Tác dụng của hàm sizeof()

The sizeof() function count all elements in an array (alias of count() function).

The following table summarizes the technical details of this function.

Return Value: Returns the number of elements in an array.
Changelog: Since PHP 7.2.0 this function yield a warning on invalid countable types.
Version: PHP 4+


The basic syntax of the sizeof() function is given with:

sizeof(array, mode);

The following example shows the sizeof() function in action.

// Sample array
$cars = array("Audi", "BMW", "Mercedes", "Volvo");
// Display array elements count
echo sizeof($cars);


The sizeof() function accepts two parameters.

Parameter Description
array Required. Specifies an array or countable object.
mode Optional. If it is set to COUNT_RECURSIVE (or 1), sizeof() will recursively count the array. This is particularly useful for counting all the elements of a multidimensional array.

Note: The sizeof() function may return 0 for a variable that isn't set, or has been initialized with an empty array. Use isset() function to test if a variable is set.

More Examples

Here're some more examples showing how sizeof() function basically works:

The following example demonstrates how to count all the elements in a multidimensional array recursively using the sizeof() function. Let's try it out and see how it works:

// Sample array
$cars = array(
    "Audi" => array("RS7", "A8"), 
    "BMW" => array("Z4", "X7", "M8"), 
    "Mercedes" => array("GLA", "GLS"),
    "Volvo" => array("XC90")

// Getting normal count
echo sizeof($cars); // Prints: 4   

// Getting recursive count
echo sizeof($cars, 1); // Prints: 12

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