How to delete the same elements in two-dimensional array in php

Deleting identical elements in a two-dimensional array is a very common task in PHP. This often requires complex calculations to determine which elements are identical before deletion can be carried out. Fortunately, PHP provides some useful functions to assist us in completing such tasks. This article will introduce some functions and techniques to help you delete identical elements in a two-dimensional array in PHP.

1. Using the array_map and array_unique functions

The array_map function applies a function to each element of an array and returns a new array. We can use array_map function and array_unique function to delete identical elements in a two-dimensional array. First, we will use the array_map function to extract all the values ​​in the 2D array. We will then use the array_unique function to remove duplicate values ​​in this new array. Finally, we will use the array_map function to remap the extracted values ​​into the format of the original 2D array.

function removeDuplicates($arr) {
    $flatten = array_map('array_values', $arr); 
    $unique_values = array_map('unserialize', array_unique(array_map('serialize', $flatten))); 
    return array_map('array_combine', array_keys($arr), array_values($unique_values));
}

This function works as follows:

We first use the array_map function to convert the two-dimensional array into a one-dimensional array. This function will return a new array, where each element represents all the values ​​in the small array, and these values ​​​​are then encapsulated in the large array. The

array_unique function removes duplicate values ​​from the $flatten array and re-indexes all numeric keys if they exist.

Later, we find that the index has been reset, so we unserialize the value, re-index it, and use the array_combine function to map it back to the original key/value pair.

2. Use foreach to traverse an array

To use foreach to traverse an array to delete the same elements, we need to traverse and create an associative array first. After getting all the values, we can use the array_unique function to remove duplicate values ​​in the array. Finally, we can use a foreach loop to repeatedly map the values.

function removeDuplicates($arr) {
    $new_arr = array();
    foreach ($arr as $key => $value) {
        $new_arr[$key] = serialize($value);
    }
    $unique_arr = array_unique($new_arr);
    foreach ($unique_arr as $key => $value) {
        $unique_arr[$key] = unserialize($value);
    }
    return $unique_arr;
}

This code will iterate through the array and add the key and a serialized array value to the $new_arr associative array. Next, we use the array_unique function to remove duplicate elements. Finally, we use foreach again to deserialize the array and redraw the index.

3. Different ways from the first value

The third method is different from the first two methods. It loops through all elements but only keeps the first value. Similarly, we can use a foreach loop to iterate over an array. For non-duplicate values ​​we will add to the $unique_arr array, otherwise we will simply skip the element.

function removeDuplicates($arr) {
    $unique_arr = array();
    foreach ($arr as $key => $value) {
        if (!in_array($value, $unique_arr)) {
            $unique_arr[$key] = $value;
        }
    }
    return $unique_arr;
}

This function iterates through all array elements and uses the in_array() function to check if they have been added to the $unique_arr array. If the element is not found, it is added to the array. The function returns an array with all identical elements removed.

Whether you are using the array_map or foreach function, these tips make it easy to delete identical elements in a 2D array in PHP. Remember to understand and use these functions so that you can work with arrays in PHP more efficiently.

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