What will happen if the array deleted by php is not displayed next time?

In PHP, array is a very common data type. It can store different types of data and can perform basic operations such as addition, deletion, modification and query. When we need to delete an array element, we can use the unset function to achieve this. But sometimes we find that the deleted element reappears in the array next time. Why is this?

In fact, this is because the array in PHP is an associative array, which means that each element has a corresponding key value, and the unset function only deletes the corresponding value, but the key still exists, so the next traversal , the key will appear in the array again, but the corresponding value will be empty.

So how can we actually delete this element? We can use the array_values ​​function to rearrange the order of the array keys so that the keys start from 0 and increase continuously. This ensures that previously deleted elements will not appear again.

The following is a sample code:

$arr = array('apple', 'banana', 'orange');
unset($arr[1]); // 删除元素
$newArr = array_values($arr); // 重新排列键
print_r($newArr);

Output result:

Array
(
    [0] => apple
    [1] => orange
)

As shown above, by using the array_values ​​function, the keys can be rearranged to ensure that the deleted elements Won't happen again.

It should be noted that although the array_values ​​function can achieve the purpose of deleting elements, it will also cause the rearrangement of the array keys, which may affect the previous code logic, so you need to consider it carefully when using it.

In addition, in PHP 7 and later versions, you can use the new function array_filter to delete array elements. This function will return a new array in which the deleted elements will not appear. Usage examples are as follows:

$arr = array('apple', '', 'banana', 'orange');
$newArr = array_filter($arr); // 过滤掉为空的元素
print_r($newArr);

Output results:

Array
(
    [0] => apple
    [2] => banana
    [3] => orange
)

The array_filter function filters out empty elements in the array without changing the key order of the original array, which has certain practicality.

In short, to delete array elements in PHP, you can use the unset function or the array_filter function to achieve it, but you need to pay attention to the order of the keys to avoid unnecessary trouble.

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