How to remove duplicates from an array in php (without using functions)

In PHP development, we often encounter scenarios where we need to deduplicate arrays. Usually we can use the array_unique function to achieve this. However, how to achieve array deduplication without using functions? This article will introduce how to use loops to achieve array deduplication.

Method 1: Use loops to implement array deduplication

The specific implementation process is as follows:

<?php //定义测试数组
$arr = array(1,2,3,2,1,4,5,4,6);
$count = count($arr);
//循环遍历数组
for ($i=0; $i<$count; $i++) {
 //从第i个元素之后循环判断是否有相同值
 for ($j=$i+1; $j<$count; $j++) {
  //如果有相同值，则删除当前元素
  if ($arr[$i] == $arr[$j]) {
   array_splice($arr, $j, 1); //使用array_splice函数删除元素
   //因为删除元素后，数组长度发生了变化，需要重新计算数组长度
   $count = count($arr);
   $j--; //指针向前移动，避免遗漏元素
  }
 }
}
//打印去重后的数组
print_r($arr);
?>

In the above code, we use a for loop to traverse the array, for each element , and then use a for loop to traverse from the elements after this element to determine whether they have the same value. If there are, use the array_splice function to remove duplicate elements and recalculate the array length and pointer position to avoid missing elements.

Method 2: Use core functions to implement array deduplication

In addition to using the loop method, we can also use PHP core functions to implement array deduplication. The specific implementation process is as follows:

<?php //定义测试数组
$arr = array(1,2,3,2,1,4,5,4,6);
//使用array_keys函数获取数组中每个元素的键值
$keys = array_keys($arr);
//使用array_values函数获取数组中每个元素的值
$values = array_values($arr);
//使用array_unique函数对values数组进行去重
$values = array_unique($values);
//使用array_combine函数将keys数组和去重后的values数组重新组成一个数组
$arr = array_combine($keys, $values);
//打印去重后的数组
print_r($arr);
?>

In the above code, we first use the array_keys and array_values ​​functions to obtain the key and value of each element in the array respectively, and use the array_unique function to deduplicate the values ​​array, and then use The array_combine function reorganizes the keys array and the deduplicated values ​​array into a new array. Although this method is relatively simple, if there are many elements, it may cause high memory usage and the performance is not as good as the loop method.

Summary:

Array deduplication is a problem often encountered in PHP development. We can use loops or core functions to achieve it. Using the loop method may be more time-consuming, but it takes up less memory and is suitable for arrays with a small number of elements. Using the core function method reorganizes the element values ​​into a new array, which takes up more memory, but can complete the deduplication operation more quickly, and is suitable for arrays with a large number of elements.

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