What is an empty array in php

phpThe empty array is an array with a length of 0. The empty array is a real object, but it contains 0 elements. In PHP, the definition of empty array is different from the null or undefined value in other programming languages. When the result returned by a variable or function is an array, you need to determine whether it is an empty array before using it. You can use empty() function or count() function to judge.

The operating system of this tutorial: Windows 10 system, PHP8.1.3 version, DELL G3 computer.

Empty array in php

An array with a length of 0 is called an "empty array". An empty array is a real object that only contains elements. The number is 0.

<?php
$arr1=array();
$arr2=[];
var_dump($arr1);
var_dump($arr2);
?>

It can be seen that the arrays $arr1 and $arr2 do not contain elements, their length is 0, and they are empty arrays.

Note: In PHP, two functions are provided to calculate the length of an array, namely the count() and sizeof() functions.

We can use these two functions to determine whether an array is an empty array.

1. Use the count() function to determine whether it is an empty array.

count($arr,$m) function is used to count all elements in the array. If the number of elements in the array is zero, then it will display an empty array.

$m: is an optional parameter and can be omitted.

If the $m parameter is omitted, or set to COUNT_NORMAL or 0, the count() function will not detect multi-dimensional arrays;

If $m is set to COUNT_RECURSIVE or 1, the count() function Will recursively count the number of elements in the array, especially useful for counting the number of elements in multi-dimensional arrays.

<?php 
header("content-type:text/html;charset=utf-8");
// 声明一个空数组
$empty_array = array();
    
// 检查数组是否为空
if(count($empty_array) == 0)
    echo "数组为空";
else
    echo "数组不为空";
?>

Output:

2. Use the sizeof() function to determine whether it is an empty array.

sizeof($arr,$m) function is an alias of count() function, that is, the function and usage of sizeof() function are exactly the same as count() function.

<?php 
header("content-type:text/html;charset=utf-8");
// 声明一个空数组
$empty_array = array();
    
if( sizeof($empty_array) == 0 )
    echo "数组为空";
else
    echo "数组不空";
?>

Output:

数组为空

Note: In PHP, the definition of an empty array is different from the null or undefined value in other programming languages. In PHP, an empty array is a special data type that represents an empty collection. Therefore, when the result returned by a certain variable or function is an array, you need to determine whether it is an empty array before using it. You can use the empty() function or count() function to judge.

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