How to determine whether a multidimensional array is empty in php

In PHP, array is one of the commonly used data types. In development, we often need to determine whether an array is empty. It is very simple to determine whether a one-dimensional array is empty. We can use the empty() or count() function to determine. But for multi-dimensional arrays, the situation is more complicated. This article will introduce how to determine whether a multi-dimensional array is empty.

1. Definition of multidimensional array
In PHP, a multidimensional array is an array containing one or more arrays. For example:

$arr = array(
       array(1, 2, 3),
       array(4, 5, 6),
       array(7, 8, 9)
);

2. Method to determine whether a one-dimensional array is empty
1. Use the empty() function to determine whether a variable is empty. When When the variable value is 0, '', null, false, array(), '0', etc., the empty() function will return true. Therefore, for a one-dimensional array, just use the empty() function to determine whether it is empty.

For example:

$arr = array('a', 'b', 'c');
if(empty($arr)){
   echo '数组为空';
}else{
   echo '数组不为空';
}

The output result is "array is not empty".

2. Use the count() function to make a judgment

The count() function can return the number of array elements. If the array is empty, it returns 0. Therefore, we can use the count() function to determine whether a one-dimensional array is empty. For example:

$arr = array('a', 'b', 'c');
if(count($arr)==0){
   echo '数组为空';
}else{
   echo '数组不为空';
}

The output result is "The array is not empty".

3. Method of judging whether a multi-dimensional array is empty

The above method is not applicable to multi-dimensional arrays. If you want to judge whether a multi-dimensional array is empty, you can use recursive method to judge.

1. Use recursion to determine whether a multi-dimensional array is empty

Recursion is a method of calling itself inside a function, which can traverse and operate multi-layer nested data structures. In PHP, we can use recursion to traverse a multi-dimensional array to determine whether it is empty.

For example:

function is_empty_array($arr){
   if(!is_array($arr)){//如果不是数组，直接返回false
      return false;
   }
   foreach($arr as $val){
      if(is_array($val)){//如果该元素是数组，则递归遍历，直到找到非数组元素
         if(!is_empty_array($val)){
            return false;
         }
      }else{//如果该元素不是数组，则判断其是否为空
         if(!empty($val)){
            return false;
         }
      }
   }
   return true;
}

The above function is used to determine whether a multi-dimensional array is empty. If it is empty, it returns true, otherwise it returns false. The foreach loop is used in the function to traverse the array elements. If the element is an array, the is_empty_array() function is called recursively to continue traversing the element; otherwise, it is judged whether the element is empty.

For example:

$arr = array(
   array(1, 2, 3),
   array(),
   array(array()),
   array(''),
   '',
   array(array())
);
if(is_empty_array($arr)){
   echo '数组为空';
}else{
   echo '数组不为空';
}

The output result is "array is empty".

In the above example, $arr contains multiple arrays, some arrays are empty, some arrays contain empty elements, and some arrays are nested arrays. Use the is_empty_array() function to easily determine whether the array is empty.

2. Use the array_filter() function to determine whether the multi-dimensional array is empty

In addition, we can also use the array_filter() function to determine whether the multi-dimensional array is empty. The array_filter() function can be used to remove empty elements from an array and return a new array. If the returned array is empty, the original array is empty.

For example:

$arr = array(
   array(1, 2, 3),
   array(),
   array(array()),
   array(''),
   '',
   array(array())
);
$new_arr = array_filter($arr);
if(empty($new_arr)){
   echo '数组为空';
}else{
   echo '数组不为空';
}

The output result is "array is empty".

In the above example, use the array_filter() function to filter out empty elements in the array and obtain a new array $new_arr. If $new_arr is empty, the original array is empty.

4. Notes

1. When traversing multi-dimensional arrays recursively, pay attention to determine whether each array element is an array.
2. When using the array_filter() function to filter an array, pay attention to the type of the return value. If you want to return the key value of the original array, you can use array_filter($arr), otherwise you can use array_values(array_filter($arr)) .

Summary

To determine whether a multi-dimensional array is empty, you need to use recursion or the array_filter() function. The recursive method is more flexible and the return value can be customized; while using the array_filter() function is simpler and more convenient, but it requires Pay attention to the type of return value. In actual development, you can choose a suitable method according to your needs.

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