How to remove duplicate data in php

php method to remove duplicate data: 1. Use the "array_unique" function to directly remove duplicate values ​​in an array; 2. Use the "array_flip" function and the "array_keys" function to remove duplicate data.

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Two kinds of PHP to remove duplicate data from arrays Method

1. Directly use the array_unique function

Use the array_unique function to directly remove duplicate values ​​​​in an array, retaining only the first occurrence of the duplicate values ​​and Its corresponding key value

Detailed instructions can be found in the PHP manual

Example 1:

$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
此时输出:
Array
(
    [a] => green
    [0] => red
    [1] => blue
)

Note: In the array_unique function, if int(3) and string( 1) When '3', the function will regard the two values ​​as the same value, and will only retain the value that appears first

Example 2:

$input = array(4, "4", "3", 4, 3, "3");
$result = array_unique($input);
var_dump($result);

At this time, it will output:

array(2) {
  [0] => int(4)
  [2] => string(1) "3"
}

2. Use the array_flip function and the array_keys function together

It is very convenient to use the array_unique function, but there is one thing, the array_unique function will not change the original key value that is retained. This In some cases, it is difficult to operate a new array. At this time, you can use the array_flip function and array_keys function

array_flip function

to swap the values ​​and key values ​​​​of the specified array. The keys become values, and the values ​​in the original array become keys, and if the same value appears multiple times, the last key becomes its value and all others are lost.

For example:

$trans = array("a" => 1, "b" => 1, "c" => 2);
$trans = array_flip($trans);
print_r($trans);

The output at this time is:

Array
(
    [1] => b
    [2] => c
)

array_keys function

array_keys function can return some or all key names in the array, this It is easier to understand. If serch_value is specified, the key value of the specified query value is returned.

For example:

$array = array(0 => 100, "color" => "red");
print_r(array_keys($array));
$array = array("blue", "red", "green", "blue", "blue");
print_r(array_keys($array, "blue"));
$array = array("color" => array("blue", "red", "green"),
               "size"  => array("small", "medium", "large"));
print_r(array_keys($array));

At this time, the output will be:

Array
(
    [0] => 0
    [1] => color
)
Array
(
    [0] => 0
    [1] => 3
    [2] => 4
)
Array
(
    [0] => color
    [1] => size
)

After introducing the two functions After use, when you encounter an array with a lot of repeated data, and want to eliminate the repeated data in the middle and start counting the key values ​​from '0', you can first use the array_flip function on the function, and then use the array_keys function on the new array. , you can achieve

Supplement: When the editor introduced the array_keys function, it suddenly occurred to me that there should be a function that can take out the values ​​​​of all arrays. After checking, there is indeed an array_value function, which can return all the values ​​​​of an array. The value is recorded into a new array, so that the key value can be counted from '0'. Therefore, if you want to achieve the purpose of this article, you can also use the array_unique function first, and then use the array_value function on it.

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