How to retain certain elements in an array and delete others in php

In PHP development, array is a very common data type. In actual development, we often encounter situations where we need to retain certain elements in an array and delete the remaining elements. This article will introduce how to use PHP language to implement this function.

1. Methods of deleting array elements

In PHP, there are many ways to delete array elements. The following are some common methods:

1. unset function

The unset function can be used to delete one or more elements in an array. Its usage is as follows:

unset($array[index]);

Among them, $array is the array variable name of the element to be deleted, and $index is the index value of the element to be deleted.

If you want to delete multiple elements, you can pass in multiple index values ​​​​in the unset function:

unset($array[index1], $array[index2], ...);

2. array_splice function

array_splice function can be used To delete some elements in the array and insert some new elements at the specified position. Its usage is as follows:

array_splice($array, $offset, $length, $replacement);

Among them, $array is the array variable name of the element to be deleted, $offset is the starting index value of the element to be deleted, $length is the number of elements to be deleted, $ replacement is the new element to be inserted.

If you just want to delete some elements without replacing them, you can set the $replacement parameter to an empty array:

array_splice($array, $offset, $length, []);

3. array_filter function

## The #array_filter function can be used to determine whether to delete an element in the array based on the specified callback function. Its usage is as follows:

array_filter($array, $callback);

Among them, $array is the name of the array variable to be filtered, and $callback is the callback function, which is used to determine which elements need to be retained and which need to be deleted.

2. Methods of retaining array elements

In the method introduced above, we discussed how to delete elements in the array, but if you want to retain some elements in the array, how to achieve it Woolen cloth?

Use the unset function

If you want to keep certain elements, you can use the unset function to delete the remaining elements. For example, if you want to keep the first three elements in the array, you can do this:

for ($i = 3; $i < count($array); $i++) {
    unset($array[$i]);
}

In this example, we use a for loop to loop through the entire array and unset the elements with index values ​​greater than 2 through the unset function delete.

Using the array_splice function

The array_splice function can also be used to retain certain elements. For example, if you want to keep the first three elements in the array, you can do this:

array_splice($array, 3);

In this example, we specified the $offset parameter as 3, which will delete all elements with index value 3 and after elements, thereby retaining the first three elements.

Using the array_slice function

The array_slice function can return a specified range of elements from an array without deleting them. For example, if you want to keep the first three elements in the array, you can do this:

$array = array_slice($array, 0, 3);

In this example, we use the array_slice function to return the first three elements in the array, and then assign them to the original array variable.

3. Sample code

The following is a complete sample code to demonstrate how to retain certain elements in the array and delete the remaining elements:

// 原始数组
$array = [1, 2, 3, 4, 5];

// 使用unset函数删除其余元素
for ($i = 3; $i < count($array); $i++) {
    unset($array[$i]);
}
print_r($array);

// 使用array_splice函数删除其余元素
$array = [1, 2, 3, 4, 5];
array_splice($array, 3);
print_r($array);

// 使用array_slice函数保留前三个元素
$array = [1, 2, 3, 4, 5];
$array = array_slice($array, 0, 3);
print_r($array);

4. Summary

In PHP development, arrays are a very common data type. For situations where we need to retain certain elements in an array and delete the rest, we can use functions such as unset, array_splice, and array_slice. These functions are all built-in functions of the PHP language and are very convenient to use.

The above is the detailed content of How to retain certain elements in an array and delete others in php. For more information, please follow other related articles on the PHP Chinese website!