How to change array length in php

In PHP programming, we often need to operate on arrays. Sometimes we need to adjust the length of the array, that is, increase or decrease the number of elements in the array. This article will introduce some methods to change the length of PHP arrays.

1. Use the array_pad function

The array_pad function can expand an array to a specified length and fill the new elements with the specified value. It accepts three parameters:

array_pad(array $array, int $size, mixed $value)

Among them, $array is the array to be changed in size, $size is the length of the expanded array, and $value is the value to be used to fill the new elements. If $size is smaller than the original array length, array_pad will not change the original elements of the array.

Here is an example of extending an array to 5 elements and filling the new elements with 0s:

$arr = array(1, 2, 3);
$arr = array_pad($arr, 5, 0);
print_r($arr); // 输出：Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 0 [4] => 0 )

2. Using the array_fill function

array_fill function You can create an array of a specified length and fill all elements with a specified value. It accepts two parameters:

array_fill(int $start_index, int $num, mixed $value)

Among them, $start_index is the starting index, $num is the array length, and $value is the value to be used to fill the elements. The following is an example to create an array of 5 elements, each element is the string "Apple":

$arr = array_fill(0, 5, "Apple");
print_r($arr); // 输出：Array ( [0] => Apple [1] => Apple [2] => Apple [3] => Apple [4] => Apple )

3. Use the array_slice function

array_slice function can intercept Part of an array and returned. It accepts three parameters:

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

Among them, $array is the array to be intercepted, $offset is the starting index, $length is the intercepted length (optional parameter), and $preserve_keys indicates whether to retain the original array. The key name (optional parameter, default is FALSE).

If the $length parameter is not specified or is NULL, all elements starting from $offset to the end of the array are intercepted.

The following is an example to delete the first element in an array:

$arr = array("one", "two", "three");
$arr = array_slice($arr, 1);
print_r($arr); // 输出：Array ( [0] => two [1] => three )

4. Use the unset function

The unset function can delete an array Elements. It accepts one parameter:

unset(mixed $var)

where $var is the variable to be deleted (can be an item in the array or the entire array). Here is an example to delete the last element in an array:

$arr = array("one", "two", "three");
unset($arr[count($arr)-1]);
print_r($arr); // 输出：Array ( [0] => one [1] => two )

Summary

The above methods can change the length of the PHP array. Use the array_pad function and array_fill function to increase the length of the array, and use the array_slice function and unset function to reduce the length of the array. Choosing the appropriate method according to the specific situation can make it more convenient to operate the array.

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