How to detect if there is a null value in an array in php

Detection steps: 1. Use the array_filter() function to filter the array and remove null elements. The syntax "array_filter (original array)" will return a filtered array; 2. Use the count() function to obtain the original array and The length of the filter array, the syntax "count (original array)" and "count (filter array)"; 3. Determine whether the original array length is equal to the filter array length, the syntax "original array length == filter array length", if equal to the array There is no null value in the array. If it is not equal, there is a null value in the array.

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

In php, you can use array_filter(), The count() function and the "==" operator are used to detect whether there are null values ​​in the array.

Implementation steps:

Step 1: Use the array_filter() function to filter the array and remove empty value elements

array_filter() function uses a callback function to filter elements in the array.

This function passes each key value in the input array to the callback function. If the callback function returns true, the current key value in the input array is returned to the result array. Array key names remain unchanged.

array array_filter ( array $array [, callable $callback [, int $flag = 0 ]] )

Parameters	Description
array	Required . Specifies the array to filter.
callback	Optional. Specifies the callback function to be used.
##flag	Yes select. Determine the parameter form received by the callback: ARRAY_FILTER_USE_KEY - callback accepts the key name as the only parameter ARRAY_FILTER_USE_BOTH - callback accepts both key name and key value

If there is no callback function, the default is to delete items with false (null) values ​​in the array, and a filtered array containing all true elements will be returned.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);  
$arr=array(&#39;foo&#39;,false,-1,null,&#39;&#39;);  
var_dump($arr);
$filte=array_filter($arr);
echo "过滤数组后：";
var_dump($filte);
?>

Step 2: Use the count() function to obtain the length of the original array and the filtered array

The count() function can return The number of elements in the array is the length of the array.

$len1=count($arr);
$len2=count($filte);

Step 3: Determine whether the length of the original array is equal to the length of the filtered array

$len1==$len2;

• If equal, there is no null value in the array (i.e. no Filter elements)

• If not equal, there are null values ​​in the array (that is, some elements have been filtered out)

Implementation Code:

function f($arr){
	$filte=array_filter($arr);
	echo "过滤数组后：";
	var_dump($filte);
	$len1=count($arr);
	$len2=count($filte);
	if($len1==$len2){
		echo "数组中没有空值<br>";
	}else{
		echo "数组中有空值<br>";
	}
}

Example 1: Call the f($arr) function

$arr=array('foo',false,-1,null,'');  
var_dump($arr);
f($arr);

Example 2:

$arr=array('foo',1,2,3);  
var_dump($arr);
f($arr);

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