How to delete duplicate element values ​​in an array in php

php method to delete duplicate values ​​in an array: 1. Use array_unique() function, syntax "array_unique(array)". 2. First use the array_flip() function to reverse the keys and values ​​of the array and remove duplicate values; then use array_flip() to reverse the array back.

The operating environment of this tutorial: windows7 system, PHP8 version, DELL G3 computer

php deletes duplicates in the array Element value

Method 1: Directly use the array_unique() function

<?php
$arr1 = array("a" => "green", "b" => "red", "c" => "green", "d" => "blue","e" =>  "red");
var_dump($arr1);
$arr2 = array_unique($arr1);
var_dump($arr2);
?>

Output:

array (size=5)
  'a' => string 'green' (length=5)
  'b' => string 'red' (length=3)
  'c' => string 'green' (length=5)
  'd' => string 'blue' (length=4)
  'e' => string 'red' (length=3)
  
array (size=3)
  'a' => string 'green' (length=5)
  'b' => string 'red' (length=3)
  'd' => string 'blue' (length=4)

Instructions:

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.

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

Syntax

array_unique(array)

Method 2: Use the array_flip() function twice

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

Output:

原始数组 :
array (size=5)
  'a' => string 'green' (length=5)
  'b' => string 'red' (length=3)
  'c' => string 'green' (length=5)
  'd' => string 'blue' (length=4)
  'e' => string 'red' (length=3)
  
更新数组 :
array (size=3)
  0 => string 'green' (length=5)
  1 => string 'red' (length=3)
  2 => string 'blue' (length=4)

Explanation:

array_flip() is a function that reverses the keys and values ​​of an array. It has a characteristic that if two values ​​​​in the array are the same, then after the reversal Keep the last key and value, and use this feature to indirectly achieve duplication of the array.

Grammar

array_flip(array);

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