How to remove duplicate values ​​from array in php?

php method to delete duplicate values ​​in an array: 1. Use array_unique() to delete duplicate values ​​in an array; 2. Use the array_flip() function to indirectly delete duplicate values ​​in an array. array_flip() reverses the array keys and values. If two values ​​in the array are the same, the last key and value will be retained after the reversal.

php method to delete duplicate values ​​from an array

1. Use array_unique ()Function

array_unique() function is used to remove duplicate values ​​from an array. If two or more array values ​​are the same, only the first value is retained and the other values ​​are removed. [Tutorial Recommendation: PHP Tutorial]

Note: The retained array will retain the key type of the first array item.

Return value: Returns the filtered array.

Code example:

<?php
$result1 = array("a" => "green", "red", "b" => "green", "blue", "red");
var_dump($result1);
$result2 = array_unique($result1);
var_dump($result2);
?>

Output:

array (size=5)
  'a' => string 'green' (length=5)
  0 => string 'red' (length=3)
  'b' => string 'green' (length=5)
  1 => string 'blue' (length=4)
  2 => string 'red' (length=3)
array (size=3)
  'a' => string 'green' (length=5)
  0 => string 'red' (length=3)
  1 => string 'blue' (length=4)

2. Use array_flip() function

array_flip() The function is used to reverse/exchange the key names in the array and the corresponding associated key values.

It has a feature that if two values ​​​​in the array are the same, then the last key and value will be retained after the inversion. Using this feature, we use it to indirectly achieve deduplication of the array.

<?php
header("content-type:text/html;charset=utf-8");
$a = array(1, 5, 2, 5, 1, 3, 2, 4, 5);
// 输出原始数组
echo "原始数组 :";
var_dump($a);
// 通过使用翻转键和值移除重复值
$a = array_flip($a);
// 通过再次翻转键和值来恢复数组元素
$a = array_flip($a);
// 重新排序数组键
$a = array_values($a);
// 输出更新后的数组
echo "更新数组 :";
var_dump($a);
?>

Output:

原始数组 :array (size=9)
  0 => int 1
  1 => int 5
  2 => int 2
  3 => int 5
  4 => int 1
  5 => int 3
  6 => int 2
  7 => int 4
  8 => int 5
更新数组 :array (size=5)
  0 => int 1
  1 => int 5
  2 => int 2
  3 => int 3
  4 => int 4

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