How to loop through an array and remove null values ​​using PHP

In PHP, it is often necessary to traverse an array and filter out useful values. However, sometimes there are some useless null values ​​in the array, and they need to be deleted to ensure the correctness of the array. This article will introduce how to use PHP to traverse an array and remove null values ​​​​from it.

1. Basic array traversal

In PHP, the easiest way to traverse an array is to use a foreach loop. The basic structure of the foreach loop is as follows:

foreach ($array as $value) {
   // 对value进行操作
}

This loop will assign each element in the $array array to the $value variable, and operate on $value in the loop body. However, this traversal method will not delete null values ​​​​in the array, and other methods need to be used for filtering.

2. Use the array_filter function

PHP provides an array_filter function, which can delete elements that do not meet the conditions in the array. Its basic usage is as follows:

$new_array = array_filter($array, 'callback');

This function will pass all elements in the $array array to the callback function callback, and then return a new array $new_array, which only contains elements for which the callback function returns a value of true . However, the callback function is too cumbersome. We can use anonymous functions to simplify the code:

$new_array = array_filter($array, function($value){
    return !empty($value);
});

This code will filter out all non-empty elements in the $array array and save them in the $new_array array.

3. Use the foreach and unset functions

Another commonly used method is to use a foreach loop and the unset function. The basic process is to loop through each element in the array, retain it if it is not empty, otherwise delete it. The code example is as follows:

foreach($array as $key => $value) {
    if(empty($value)) {
        unset($array[$key]);
    }
}

This code first uses a foreach loop to traverse each element in the $array array, and uses an if statement to determine whether $value is empty. If it is empty, use the unset function to remove the element from the $array array.

Although this method is simple and straightforward, using the unset function during the loop may cause performance problems and is not suitable for large arrays.

4. Using the array_walk function

The array_walk function can use the callback function to process each element in the array. During use, we can modify the original array by passing by reference. The basic usage is as follows:

function removeEmpty(&$value, $key){
    if(empty($value)){
        unset($value);
    }
}
array_walk($array, 'removeEmpty');

This code defines a callback function removeEmpty, which uses reference transfer to pass $value to the function. Inside the function, it is judged whether $value is empty. If it is empty, unset is used. function to remove it from the array. Finally, use the array_walk function to apply the removeEmpty function to the $array array to remove the null values ​​​​in it.

5. Summary

This article introduces several methods of traversing an array and removing null values ​​​​in PHP. The most convenient and quick one is to use the array_filter function. If you need to delete null values ​​directly during the loop, you can use the foreach and unset functions or the array_walk function. Using these methods, you can clean array data and ensure the correctness of the data.

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