How to clear null values ​​in php array

In PHP development, we often need to process array data, and clearing the null values ​​​​is a common task. A null value can refer to an empty string, a null value, or an undefined value. In this article, we will explore how to clear null values ​​from an array using PHP functions.

1. PHP function array_filter()

PHP provides an array_filter() function, which can filter the array and return a new filtered array. You can pass a callback function to determine which values ​​are retained.

When using the array_filter() function to clear empty values ​​​​in an array, you need to pay attention to the following two points:

1. Pass the callback function: Because the filtering conditions are different, we need to pass a callback function to judge. Whether the current array element is null. The callback function can be customized to determine whether to retain each array element by judging the element. The following is a sample code that uses a custom callback function to clear empty values ​​in the array:

function removeEmptyValues($value) {
    return !empty($value) || $value === 0;
}

$array = array("", "test", null, " ", 0, "0");
$result = array_filter($array, "removeEmptyValues");

print_r($result);

The output result is:

Array
(
    [1] => test
    [3] =>  
    [4] => 0
    [5] => 0
)

The removeEmptyValues() function here determines whether the array element is Empty string, null value, 0 to determine whether to retain the element. Note that you need to use === instead of == to strictly compare 0 and the empty string.

2. Pass the array key name: By default, when using the array_filter() function to clear the null values ​​​​in the array, the function will re-index the new array, that is to say, the key name in the original array may will be deleted. If you want to retain the key name of the original array, you should pass the array key name to the callback function, as follows:

function removeEmptyValues($key, $value) {
    return !empty($value) || $value === 0;
}

$array = array("name" => "", "age" => null, "sex" => "male");
$result = array_filter($array, "removeEmptyValues", ARRAY_FILTER_USE_BOTH);

print_r($result);

The output result is:

Array
(
    [sex] => male
)

In the callback function, we Two parameters, $key and $value, are passed. $key represents the key name of the current array element, and $value represents the value of the array element. In this case, we need to add the third parameter ARRAY_FILTER_USE_BOTH, which means using the callback function to pass the key name and key value.

2. Use foreach()

In addition to the array_filter() function, we can also use the foreach() loop to clear null values ​​​​in the array. This method cycles through the array elements one by one to clear the null values. The following code demonstrates how to use foreach() to clear null values ​​​​in an array:

$array = array("", "test", null, " ", 0, "0");
$result = array();

foreach ($array as $value) {
    if (!empty($value) || $value === 0) {
        $result[] = $value;
    }
}
print_r($result);

The output result is:

Array
(
    [0] => test
    [1] =>  
    [2] => 0
    [3] => 0
)

This method loops through the array elements and uses if statements to determine the elements Whether it is a null value, if not it is added to a new array.

3. Use the array_map() function

PHP also provides another function array_map(), which can apply the specified callback function to each element in the array and return a new array . We can clear null values ​​from the array by passing a callback function. The following is a sample code that uses the array_map() function to clear the empty value of the array:

function removeEmptyValues($value) {
    return !empty($value) || $value === 0;
}

$array = array("", "test", null, " ", 0, "0");
$result = array_map("removeEmptyValues", $array);

print_r($result);

The output result is:

Array
(
    [0] => 
    [1] => test
    [2] => 
    [3] =>  
    [4] => 
    [5] => 0
)

Note that when using the array_map() function to clear the empty value of the array, the original array The index key name will not be retained, so only the value of the element is retained in the output result.

Summary

In PHP development, we often need to clear null values ​​​​in arrays. This article introduces three common methods: using array_filter(), foreach() loop, and array_map() function. Among them, the array_filter() function is the most widely used among the three methods, and the callback function can be customized to meet different needs. If you need to retain the key names of the original array, you can use the third parameter of array_filter() or a custom callback function and pass the key name and key value as two parameters. If you need to retain the key names and indexes of the original array, you can use foreach() to loop through the array and determine whether the elements are null one by one. When using the array_map() function to clear null values, note that the index key names of the output array may be reset, so if you need to retain the key names of the original array, you need to handle it separately.

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