How to delete array key in php

In PHP development, array is a very common data type that can store any type of data. However, when using an array, sometimes you need to delete an element. In this case, you need to delete the array key corresponding to the element. This article will introduce several methods to delete array keys in PHP.

1. unset function

The unset function in PHP can be used to delete variables. Use the unset function to completely delete a variable or delete an element in an array. For example, the following code deletes the first element in the array $numbers:

$numbers = array(0, 1, 2);
unset($numbers[0]);

Be careful when using the unset function to delete array elements. If an element in the array is deleted, its original key will also be deleted, which will cause the keys in the array to be discontinuous. For example, if you delete the first element in the $numbers array, its key will become 1 instead of 0.

2. array_splice function

The array_splice function in PHP can be used to delete elements from an array and return the deleted elements. Its first parameter is the array of elements to be deleted, the second parameter specifies the index to start deleting from the array, and the third parameter specifies the number of elements to be deleted. For example, the following code deletes the first two elements in the array $numbers:

$numbers = array(0, 1, 2);
array_splice($numbers, 0, 2);

Use the array_splice function to keep the keys in the array continuous, and the keys of deleted elements will be reordered.

3. array_filter function

The array_filter function in PHP can be used to remove certain elements from an array and only retain elements that meet the conditions. This function accepts an array parameter and a callback function parameter. The callback function is used to determine whether each element in the array should be retained. For example, the following code can remove odd-numbered elements from the array $numbers:

$numbers = array(0, 1, 2, 3, 4, 5);
$numbers = array_filter($numbers, function($num) {
return $num % 2 == 0; // Only keep even elements
});

Using the array_filter function can easily select the array elements to keep, but A callback function needs to be written.

Summary

This article introduces several methods to delete array keys in PHP, including using the unset function, array_splice function and array_filter function. Use the unset function to directly delete array elements, but it will cause the keys in the array to be discontinuous; use the array_splice function to keep the keys in the array continuous, but you need to specify the number of elements to be deleted; use the array_filter function to easily select the elements to keep Array elements, but you need to write a callback function. Choosing different methods depends on the specific application scenario.

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