How to convert null value in array in php

In PHP, arrays are a very common data type, and there may be some null values ​​in these arrays. If we want to process these arrays, sometimes we need to convert these null values ​​into other values. So how to implement null value conversion in an array in PHP? Let’s introduce it below.

1. What is null value?

In PHP, null is a special value, which means no value and empty. If the value of a variable is null, then the variable is empty, that is, it does not contain any value.

In the array, if the value of a key-value pair is null, it means that the key-value pair does not contain any value.

For example:

$arr = array(
    "key1" => null,
    "key2" => "value2",
    "key3" => null
);

2. Why should you convert null values ​​into other values?

In PHP, sometimes we need to process key-value pairs in an array. For example, we may need to convert the null value in the array into an empty string or other default value. In this case, we need to use some specific methods.

3. How to convert the null value in the array into other values?

In PHP, you can use some built-in functions or custom functions to convert null values ​​in the array. Let’s introduce them separately below.

1. Use the PHP built-in function array_filter()

The array_filter() function in PHP can filter the elements in the array and return a new array that does not contain elements with specified conditions. When the filter condition is null, all null values ​​in the array are filtered out.

For example:

$arr = array(
    "key1" => null,
    "key2" => "value2",
    "key3" => null
);
$new_arr = array_filter($arr);
print_r($new_arr);

The output result is:

Array(
    [key2] => value2
)

As can be seen from the above example, the array_filter() function can be used to filter out the null values ​​​​in the array and return values ​​that do not contain A new array of null values.

2. Use the PHP built-in function array_map()

The array_map() function in PHP can apply all array elements to the specified callback function and return the result as a new array.

We can customize a callback function to convert the null value into the default value. The following example:

$arr = array(
    "key1" => null,
    "key2" => "value2",
    "key3" => null
);
$new_arr = array_map(function($value) {
    return $value ?? ''; //将null值转换成空字符串
}, $arr);
print_r($new_arr);

The output result is:

Array(
    [key1] => 
    [key2] => value2
    [key3] => 
)

As can be seen from the above example, using the array_map() function can convert the null value in the array into the value we want.

3. Custom function

In PHP, we can also customize a function to convert the null value in the array.

For example, we can customize a function null_to_str() to convert the null value in the array into an empty string. The following example:

function null_to_str($arr) {
    foreach ($arr as $key => $value) {
        if (is_null($value)) {
            $arr[$key] = '';
        }
    }
    return $arr;
}

$arr = array(
    "key1" => null,
    "key2" => "value2",
    "key3" => null
);
$new_arr = null_to_str($arr);
print_r($new_arr);

The output result is:

Array(
    [key1] => 
    [key2] => value2
    [key3] => 
)

As you can see from the above example, you can also use a custom function to convert the null value in the array into the value we want.

4. Summary

In PHP, there are many ways to convert null values ​​in an array into other values. We can use PHP's built-in functions array_filter(), array_map(), etc., or we can customize a function to perform conversion. Different conversion methods have different uses and need to be selected according to the actual situation.

If we need to filter or convert the null values ​​​​in the array, we can refer to the method introduced above for processing. The converted new array can meet our needs for array use.

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