Practical tips for PHP functions: array_slice()

PHP is a commonly used Web development language. It provides many commonly used functions and methods to help us complete programming tasks more quickly. In PHP programming, arrays are also an essential part, and in arrays, the array_slice() function is a very practical function. This article will introduce the usage of array_slice() function and some practical skills.

1. Basic use of array_slice() function

The function of array_slice() function is to return a part of an array, that is, to extract a new array from the array. The new array includes the data from the specified position. The specified number of elements to start with.

Basic syntax of array_slice() function:

array array_slice ( array $array , int $offset [, int $length = NULL [, bool $preserve_keys = FALSE ]] )

Among them, $array is the source array, $offset is the starting position of extraction, $length is the length of extraction, $preserve_keys indicates whether to retain the original Array key-value pair relationship.

The following is a simple example:

$arr = array('a', 'b', 'c', 'd', 'e');
$part = array_slice($arr, 2, 2);
print_r($part);

Output:

Array
(
    [0] => c
    [1] => d
)

In this example, the source array $arr consists of 5 elements. Use the array_slice() function to extract 2 elements starting from the 3rd element, and get a new array $part.

2. Practical skills of array_slice() function

1. Extract from the end

In some scenarios, if we want to start from the end of the array To extract a part of elements, you can set $offset to a negative number, which means counting from the end.

For example, if you want to extract the last three elements of the array, you can do this:

$arr = array('a', 'b', 'c', 'd', 'e');
$part = array_slice($arr, -3);
print_r($part);

Output:

Array
(
    [2] => c
    [3] => d
    [4] => e
)

2. Extract the element with the specified key name

Sometimes, we not only need to extract a part of the elements of the array, but also need to extract the elements with the specified key name. At this time, you can use the array_flip() function to swap the keys and values ​​of the array, and then use the array_intersect_key() function to extract the element with the specified key name.

For example, if you want to extract the elements with key names 2 and 4 in the array, you can do this:

$arr = array('a', 'b', 'c', 'd', 'e');
$keys = array(2, 4);
$flipped = array_flip($arr);
$selected = array_intersect_key($flipped, array_flip($keys));
$part = array_intersect_key($arr, $selected);
print_r($part);

Output:

Array
(
    [2] => c
    [4] => e
)

In this example, use array_flip( ) function swaps the keys and values ​​of the $num array to obtain a new array $flipped with the array element value as the key name. Then use the array_intersect_key() function to extract the element with the specified key name, and obtain a new array $selected containing the element with the specified key name. Finally, use the array_intersect_key() function and the original array $arr to extract the corresponding elements, and obtain a new array $part containing the specified elements.

3. Delete specified elements

Sometimes, we want to delete certain elements in an array instead of extracting them. At this time, you can use the array_splice() function to extract the elements to be deleted and delete them.

For example, if you want to delete 2 elements starting from the 2nd element in the array, you can do this:

$arr = array('a', 'b', 'c', 'd', 'e');
$part = array_splice($arr, 2, 2);
print_r($arr);

Output:

Array
(
    [0] => a
    [1] => b
    [4] => e
)

In this example, Use the array_splice() function to extract the 2 elements starting from the 3rd element and delete them from the original array $arr.

4. Conclusion

The array_slice() function is a very practical function and is very convenient to use. Mastering the usage and techniques of the array_slice() function is very helpful for writing more efficient PHP programs.

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