How to delete null value pairs in two-dimensional array in php

When developing using PHP, we often encounter the need to operate arrays. Array is a common data structure and is also widely used in PHP. A two-dimensional array is a special type of array whose elements are also arrays. In actual development, we sometimes need to delete null value pairs in a two-dimensional array, which requires using some PHP array functions to achieve this.

1. What is a two-dimensional array

If the elements of an array are also an array, then the array is a two-dimensional array. In PHP, a two-dimensional array can be defined in the following way:

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

The above code creates a two-dimensional array containing 3 elements, each element is a one-dimensional array containing 3 elements.

2. Delete null value pairs in two-dimensional arrays

In actual development, we sometimes need to delete null value pairs in two-dimensional arrays. The so-called null value pair means that the value corresponding to a key in the array is an empty string, null, 0 or no value. We can use PHP's various array functions to achieve this purpose.

1. Use the array_filter function to filter

The array_filter function can be used to filter all null value pairs in an array. Its first parameter is the array that needs to be filtered. The two parameters are a callback function used to filter each element in the array.

function filterEmpty($arr) {
    foreach($arr as $key=>$value) {
        if(is_array($value)) {
            $arr[$key] = filterEmpty($value);
        }
    }

    return array_filter($arr);
}

$arr = array(
    array(1,'',3),
    array(4,5,''),
    array(0,8,null)
);

$arr = filterEmpty($arr);
var_dump($arr);

The above code defines a filterEmpty function to filter null value pairs in a two-dimensional array. It uses a recursive function to traverse each element in the array. If the element itself is an array, the filterEmpty function itself is called to continue. Carry out traversal. Next, use the array_filter function to filter each element to obtain an array that does not contain null value pairs.

2. Use the array_walk function

The array_walk function can iterate each element in the array and perform specific operations on it. We can define a callback function to judge each element and delete the null value pairs.

function walkEmpty(&$value, $key) {
    if(is_array($value)) {
        $value = array_filter($value);
    }

    if(empty($value)) {
        unset($value);
    }
}

$arr = array(
    array(1,'',3),
    array(4,5,''),
    array(0,8,null)
);

array_walk($arr, 'walkEmpty');
var_dump($arr);

The above code defines a walkEmpty function as a callback function, and uses the array_walk function to traverse each element in the $arr array and judge it. If the element is an array, first use the array_filter function to filter null value pairs in the array. Next, determine whether the element is empty. If it is empty, use the unset function to delete the element from the array.

3. Use foreach loop to traverse the array

We can also use foreach loop to traverse the array and judge each element.

function deleteEmpty($arr) {
    foreach($arr as $key=>$value) {
        if(is_array($value)) {
            $arr[$key] = deleteEmpty($value);
        }

        if(empty($value)) {
            unset($arr[$key]);
        }
    }

    return $arr;
}

$arr = array(
    array(1,'',3),
    array(4,5,''),
    array(0,8,null)
);

$arr = deleteEmpty($arr);
var_dump($arr);

The above code defines a deleteEmpty function, which uses a foreach loop to traverse each element in the $arr array and judge it. If the element is an array, call the deleteEmpty function itself to continue traversing. Next, determine whether the element is empty. If it is empty, use the unset function to delete the element from the array.

3. Summary

Two-dimensional array is a common data structure that is often used in PHP development. Deleting null value pairs in a two-dimensional array is also a common operation. The above article introduces three implementation methods, using the array_filter function, array_walk function, and foreach loop to traverse the array. We can choose the method that suits us based on our specific needs.

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