What is the difference between count() and sizeof() functions in PHP ?

The collection objects in PHP are characterized by a length parameter to indicate the number of elements contained within it. It is necessary to estimate the length of an array in order to perform array manipulations and modifications. 

sizeof() Method

The sizeof() method is used to calculate all the elements present in an array or any other countable object. It can be used for both uni-dimensional as well as multi-dimensional arrays. The sizeof() method takes a longer execution time. Also, the sizeof() method is an alias of the count() method.

Syntax

sizeof(arr, mode);

Parameters

This method accepts two parameters that are discussed below:

• arr – The array to count the elements.
• mode – Indicator to check whether or not to count all the elements –
  • 0 – Default. Does not count all elements of multidimensional arrays
  • 1 – Counts the array recursively (counts all the elements of multidimensional arrays).

Example: This example describes the basic usage of the sizeof() method in PHP.

PHP

<?php
$arr = array(
    "Java" => array(
        "SpringBoot",
        "Eclipse"
    ) ,
    "Python" => array(
        "Django"
    ) ,
    "PHP" => array(
        "CodeIgniter"
    )
);

print_r($arr);
print ("<br>");

echo "Sub elements of an array: "
      . sizeof($arr) . "<br>";
echo "All elements of an array: "
      . sizeof($arr, 1);

?>

Output:

Array ( 
    [Java] => Array ( 
        [0] => SpringBoot 
        [1] => Eclipse 
    ) 
    [Python] => Array ( 
        [0] => Django 
    ) 
    [PHP] => Array ( 
        [0] => CodeIgniter 
    ) 
)
Sub elements of an array: 3
All elements of an array: 7

count() Method

The count() method is used to calculate all the elements in the array or any other countable object. It can be used for both uni-dimensional as well as multi-dimensional arrays.

Syntax

count(arr, mode);

Parameters

This method accepts two parameters that are discussed below:

• arr – The array to count the elements.
• mode – Indicator to check whether or not to count all the elements –
  • 0 – Default. Does not count all elements of multidimensional arrays
  • 1 – Counts the array recursively (counts all the elements of multidimensional arrays).

Example: This example describes the basic usage of the count() Method in PHP.

PHP

<?php
$arr = array(
    "Java" => array(
        "SpringBoot",
        "Eclipse"
    ) ,
    "Python" => array(
        "Django"
    ) ,
    "PHP" => array(
        "CodeIgniter"
    )
);

print_r($arr);
print ("<br>");

echo "Sub elements of an array: "
      . count($arr) . "<br>";
echo "All elements of an array: "
      . count($arr, 1);

?>

Output

Array ( 
    [Java] => Array ( 
        [0] => SpringBoot 
        [1] => Eclipse 
    ) 
    [Python] => Array ( 
        [0] => Django 
    ) 
    [PHP] => Array ( 
        [0] => CodeIgniter 
    ) 
)
Sub elements of an array: 3
All elements of an array: 7

Difference between sizeof() and count() Methods

	sizeof() Method	count() Method
1.	The sizeof() function is used to return the number of elements in an array.	The count() returns the number of elements in the array.
2.	Its syntax is -: sizeof(array, mode)	Its syntax is -: count(array, mode)
3.	Its return value is of integer type.	Its return value is of integer type.
4.	This function is an alias of the count() function.	The count() function may return 0 for a variable that is not set.
5.	It is supported in PHP version 4.0+	It is supported in PHP version 4.0+

In conclusion, there is no difference between the count() and sizeof() methods of PHP. One method is the alias of another method. As sizeof() method execution time is longer, so count() method is considered to be better and faster.