php delete key

In modern development, PHP language has become one of the preferred languages ​​for many people to develop web pages. Many people use PHP language to store and retrieve data. In PHP, array (Array) is a very useful function, but sometimes it is necessary to remove specific data. At this time, you need to delete the data key.

This article will introduce the following content:

1. Array (Array) in PHP
2. What is key
3. Use the unset() function to delete the key The implementation method
4. The implementation method of using the array_filter() function to delete the key
5. The difference, advantages and disadvantages of the two methods
6. Array (Array) in PHP

PHP is an interpreted scripting language, and the array types it supports are relatively complex. In PHP, the basic concept of an array is a set of values ​​guided by a specific key. Each value of the array has an associated key that is used to access that value.

For example, we can first define an array $fruits, which contains 3 elements (count of three fruits):

$fruits = array("apple" => 2, "banana" => 3, "orange" => 4);

We can use the key names "apple", "banana", "orange" to access the corresponding key values ​​2, 3, 4 . Can be accessed with the following statement:

echo $fruits["apple"];
//Output 2

2. What is key

us When an array is created, a key is added, and the key can be viewed as an element in the array. For example, in the array defined above, "apple", "banana", and "orange" are the keys. The key value can be a string or a number. Some other values ​​can also be used, such as null. However, we only mention strings and numbers here.

3. How to use the unset() function to delete key

In PHP, we can use the unset() function to delete the array element we specify, that is, delete Corresponding key.

The following uses an example to explain in detail how to use this function:

$fruits = array("apple" => 2, "banana" => 3, "orange" = > 4);

print_r($fruits);
//Output Array ( [apple] => 2 [banana] => 3 [orange] => 4 )

unset($fruits["banana"]);

print_r($fruits);
//Output Array ( [apple] => 2 [orange] => 4 )

Tip: Using the unset() function will directly affect the original array. In the example above, unset($fruits["banana"]); deletes the element with the "banana" key, and the "banana" key of the original $fruits array has been deleted.

4. How to use the array_filter() function to delete keys

In addition to using the unset() function, PHP also provides other functions to delete keys in the array. We can use PHP's built-in array_filter() function to achieve this function. This function does not directly affect the original array, but returns a new array in which the specified element has been deleted.

The following is an example to illustrate:

$fruits = array("apple" => 2, "banana" => 3, "orange" => 4);

$fruits = array_filter($fruits, function($k) {

return $k != "banana";

}, ARRAY_FILTER_USE_KEY);

print_r($fruits);
//Output Array ( [apple] => 2 [orange] => 4 )

In the above example, we use the array_filter() function to retain elements that are not "banana" and assign the result to the original array . This operation does not directly affect the original array.

5. The differences, advantages and disadvantages of the two methods

In the above two methods, the direct impact of the unset() function is sometimes not what we want. In a real project, this could result in accidental deletion of data.

The array_filter() function will not directly affect the original array and return it as a new array. However, it should be noted that this function still requires a callback function to implement the filtering function, which will cause a waste of space.

When using these two methods, you need to choose the method that is more suitable for you according to your actual needs. If you want to directly affect the original array, you can use the unset() function; if you need to filter the array and return a new array, you can use the array_filter() function.

In short, no matter which method is used, you can efficiently delete the specified key in the array in PHP. This is a very practical skill for many PHP developers, especially when dealing with huge amounts of data. I hope this article can help everyone when developing.

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