How to remove duplicate values ​​from php array

PHP arrays are containers used to store the same type of data. However, sometimes we accidentally add duplicate values ​​​​in the array, and these duplicate values ​​​​will bring us unnecessary trouble. In this article, we will introduce how to use PHP language to remove duplicate values ​​​​from an array.

1. Use the array_unique() function in PHP to remove duplicate values ​​

array_unique() is a function in PHP that is used to remove duplicate values ​​from an array. Using this function can easily remove duplicate values ​​from the array. The code is as follows:

$arr = array("a", "b", "c", "d", "b", "c"); //定义一个含有重复值的数组
$arr = array_unique($arr); //将数组中的重复值去掉
print_r($arr); //输出去重后的数组

In the above code, the $arr array contains duplicate values ​​"b" and "c", and then we use array_unique () function removes these duplicate values, and finally outputs the deduplicated array, that is:

Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
)

2. Use the for loop and if statement in PHP to remove duplicate values ​​

In addition to using array_unique () function, we can also use for loops and if statements to traverse the array and remove duplicate values. The code is as follows:

$arr = array("a", "b", "c", "d", "b", "c"); //定义一个含有重复值的数组
$new_arr = array(); //定义一个新的空数组
for($i = 0; $i < count($arr); $i++) {
    if(!in_array($arr[$i], $new_arr)) { //判断$new_arr数组中是否已经存在该元素
        array_push($new_arr, $arr[$i]); //如果不存在，则将该元素加入$new_arr数组中 
    }
}
print_r($new_arr); //输出去重后的数组

In the above code, we first define an array containing duplicate values array $arr, and then defines a new empty array $new_arr. Next, we use a for loop and if statement to traverse the array $arr. If an element does not exist in $new_arr, then add the element to the new array, and finally output the deduplicated $new_arr array, that is:

Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
)

3. Use the array_flip() function and array_keys() function in PHP to remove duplicate values

Another clever way is to use the array_flip() function and array_keys() function in PHP to remove duplicate values. value, the specific code is as follows:

$arr = array("a", "b", "c", "d", "b", "c"); //定义一个含有重复值的数组
$arr = array_flip($arr); //使用array_flip()函数将数组中的值和键进行互换
$arr = array_keys($arr); //使用array_keys()函数提取数组中的键
print_r($arr); //输出去重后的数组

In the above code, we first use the array_flip() function to exchange the key value of the array $arr containing repeated values, and then use the array_keys() function to extract the keys in the array Key, you can get the deduplicated array, and finally output it, that is:

Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
)

Summary:

PHP array is a very commonly used data type, but when using the array, there will be Encountered a problem with duplicate values. This article introduces three methods for removing duplicate values ​​​​in arrays. Different methods can be selected according to the specific actual needs. The most convenient one is the array_unique() function, and the most clever one is to use the array_flip() function and array_keys() function. These methods can help us handle duplicate values ​​​​that exist in PHP arrays more effectively and improve the efficiency of the program.

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