How to determine an empty array in php

In PHP, to determine whether a variable is empty, you can usually use the empty() function or isset() function. However, for an array, it does not necessarily apply to all situations.

In PHP, an empty array can refer to an array with no elements, or it can be a completely undefined array. Therefore, you need to pay attention when using the empty() function or isset() function to determine an empty array.

1. Use the empty() function

When the empty() function determines whether the array is empty, you need to pay attention to the following two points:

a. The array is not defined Return true

If an array is not defined, that is, it is not assigned a value or is assigned a value of null, then using the empty() function on the array will return true.

For example:

$undefined_arr = null;   
var_dump(empty($undefined_arr)); //true

b. Returns true only if the array has no elements

If an array is defined but does not have any elements, then use empty for the array () function will return true.

For example:

$empty_arr = array();
var_dump(empty($empty_arr)); //true

According to the above characteristics, accurate judgment can be made by combining the isset() function.

2. Use the isset() function

isset() function needs to pay attention to the following two points when judging whether an array is empty:

a. Only the array is undefined Returns false in case

If an array is not defined, that is, it is not assigned a value or is assigned a value of null, then using the isset() function on the array will return false.

For example:

$undefined_arr = null;
var_dump(isset($undefined_arr)); //false

b. Returns true when there are elements or is defined using the array() function

If an array is defined, it will be returned regardless of whether there are elements or not. true.

For example:

$empty_arr = array();
$has_element_arr = array('1', '2');
var_dump(isset($empty_arr)); //true
var_dump(isset($has_element_arr)); //true

Therefore, the isset() function can be used in conjunction with the empty() function to accurately determine whether an array is empty:

$arr = array();
if(isset($arr) && !empty($arr)){
    echo '数组不为空';
} else {
    echo '数组为空';
}

Here, we We have already learned about several methods of judging empty arrays in PHP. Choosing different methods according to different situations can more accurately judge whether an array is empty.

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