How to delete duplicate arrays in php (without built-in functions)

PHP is a widely used scripting language with a powerful built-in function library that can easily implement many functions needed in daily development. However, in some cases, we may need to implement some functions that do not use built-in functions, which requires us to have an in-depth understanding and mastery of the basics of the PHP language. This article will discuss how to remove duplicate arrays in PHP without using built-in functions.

1. Background of the problem

In actual development, we often need to process arrays, and sometimes we need to remove duplicate elements in the array. This problem is very easy to solve if you use built-in functions. PHP provides many functions for deduplication, such as array_unique, array_count_values, etc. But in some cases, we may need to manually implement the deduplication function ourselves. For example, in an exam or interview, you may be faced with a situation where you are not allowed to use built-in functions and can only implement the function manually. Therefore, in this article, we will discuss how to implement deduplication function manually with PHP.

2. Method explanation

The basic idea of ​​​​implementing the function is as follows:

1. Traverse the original array and add each element to the new array (if the element is in the new array does not exist).

2. Use the in_array function to determine whether the element appears in the new array.

3. If the element appears in the new array, no operation will be performed.

4. If the element does not appear in the new array, add it to the new array.

The following is the specific implementation code:

<?php function deleteRepeat($arr)
{
    $newArr = array();
    foreach($arr as $value){
        if(in_array($value,$newArr)){
            continue;
        }else{
            $newArr[] = $value;
        }
    }
    return $newArr;
}
?>

In this function, we first declare a new empty array $newArr. Then use a foreach loop to traverse the original array $arr. Use the in_array function in the loop body to determine whether each element appears in $newArr. If the element appears in $newArr, use the continue statement to skip this loop. Otherwise, use the [] operator to add the element to $newArr. Finally, the new array $newArr is returned.

3. Test

In order to verify whether our function is valid, we need to test it. The following code demonstrates how to use our function to remove duplicate elements from an array:

<?php $arr = array(3,6,9,6,3,8,1);
$newArr = deleteRepeat($arr);
print_r($newArr);
?>

The output result is:

Array ( [0] => 3 [1] => 6 [2] => 9 [3] => 8 [4] => 1 )

As you can see, the function successfully removes duplicate elements from the original array.

4. Summary

In this article, we discussed how to manually implement the function of deduplicating arrays in PHP. Since PHP has many built-in functions for deduplication, many developers may find it redundant to implement this function manually. However, in some cases, it is important to know how to implement this functionality manually, as it demonstrates your mastery of the basics of the PHP language. At the same time, manually implementing the deduplication function can also help us better understand the workflow of array operations in PHP, which is also of great help to our code optimization and debugging during development.

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