How to remove duplicates in php without array function

PHP language is a very popular programming language today. Its powerful array function functions have been mastered and used by more and more programmers during the development process. However, young PHP programmers may not know that the PHP language does not require the use of array functions to perform array deduplication operations. In this article, we will explore various methods of array deduplication in the PHP language, and understand and master its implementation principles.

Array deduplication is a basic data operation that can effectively remove duplicate data and save storage space and computing resources for developers. In PHP, we usually use array functions such as array_unique to perform deduplication operations, but in fact, some language features built into the PHP language can be used to achieve the same function, and these methods are more efficient and flexible than using arrays. function to remove duplicates.

Method 1: Use the key-value exchange principle to achieve array deduplication

In PHP, arrays are in the form of key-value pairs, and the corresponding values ​​can be accessed directly through the key name (Key) (Value), and the key name can be any integer or string. Therefore, we can use this feature to achieve the purpose of deduplication by exchanging the values ​​and key names of the array. The specific implementation method is as follows:

<?php
//需要去重的数组
$origin = array(1, 2, 3, 3, 4, 4, 5);

//数组去重核心代码
foreach ($origin as $key => $val) {
    $tmp[$val] = 1;
}
$unique = array_keys($tmp);

//输出结果
print_r($unique);
?>

In this code, we first use a foreach loop to traverse the array, using the corresponding value as the key name and 1 as the corresponding value. Because the key name is unique, different values ​​will be assigned to different key names, and the same value will overwrite the original key name, thereby achieving the purpose of deduplication. Finally, all key names are extracted through the array_keys function and formed into a new array.

Method 2: Use the array_flip function to exchange key names and values ​​to achieve array deduplication

Compared with the above method 1, this deduplication method is more concise. We can use PHP's built-in array function array_flip to exchange the key names and values ​​of the original array to achieve the effect of deduplication.

<?php
//需要去重的数组
$origin = array(1, 2, 3, 3, 4, 4, 5);

//数组去重核心代码
$unique = array_keys(array_flip($origin));

//输出结果
print_r($unique);
?>

In this code, we first use the array_flip function to swap the key names and value positions of the original array, so that the repeated values ​​become repeated key names, and the key names must be unique. Therefore, the effect of deduplication is achieved. Finally, we use the array_keys function again to extract all key names and generate a new deduplicated array.

Method 3: Use the array_diff function to perform array difference operation

This deduplication method is different from the first two methods. It deduplicates by calculating the array difference. The specific implementation method is as follows:

<?php
//需要去重的数组
$origin = array(1, 2, 3, 3, 4, 4, 5);

//数组去重核心代码
$unique = array_diff($origin, array_diff_assoc($origin, array_unique($origin)));

//输出结果
print_r($unique);
?>

In this code, we first use the array_unique function to obtain the deduplicated array. Then, we use the array_diff_assoc function to compare the original array and the deduplicated array, and get the parts where their key names and key values ​​are different, which are the duplicate parts. Finally, we use the array_diff function again to remove duplicate parts and get the final deduplicated array.

To sum up, we have discussed three array deduplication methods built into the PHP language. All methods have their own advantages and applicable scenarios. Flexible mastery of these methods can save us time, save resources, and improve the readability and maintainability of the code. Therefore, programmers should choose different deduplication methods according to specific situations in daily development to ensure the efficient operation of the code.

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