How to start php array subscript from 1

In PHP, the default array subscripts start from 0. However, in some scenarios, it may be necessary to change the array subscript to start from 1. This article will introduce 3 methods to achieve this requirement.

Method 1: Manually modify the array subscript

Manually modifying the array subscript is the simplest method. When defining the array and filling in data, just increase the subscript starting from 1. For example:

$arr = array(
    1 => '第一个元素',
    2 => '第二个元素',
    3 => '第三个元素'
);

After processing in this way, the subscripts of the array become 1, 2, and 3.

It should be noted that when changing the array subscript to start from 1, the subscript must be specified manually. The array cannot be filled in the default way, otherwise the subscript will still start from 0.

Method 2: Change the array pointer

In PHP, you can use the reset function to reset the array pointer to the first element, and use the end function to move the array pointer to the last element. If you can move the array pointer to -1, that is, before the 0th element, you can change the array subscript to start from 1.

Code example:

$arr = array('第一个元素', '第二个元素', '第三个元素');
end($arr);     // 移动到最后一个元素
$idx = key($arr);     // 保存最后一个元素的下标
reset($arr);     // 将指针重置到第一个元素
$i = 0;
while(key($arr) !== $idx) {
    $i++;
    next($arr);     // 指针后移
    $arr_new[$i] = current($arr);     // 保存当前元素到新数组
}
$arr_new[1] = $arr[0];     // 将第0个元素移动到下标为1的位置

The above code will change the subscript of the array $arr to start from 1.

It should be noted that this method is relatively inefficient because it requires moving the pointer multiple times. And if the 0th element of the array exists, special processing is required.

Method 3: Use array_combine function

The array_combine function can use one array as the subscript and another array as the value to create a new associative array. If you use 0, 1, 2, and 3 as the subscript array and the value of the original array as the value array, you can change the subscript to start from 1.

Code example:

$arr = array('第一个元素', '第二个元素', '第三个元素');
$arr_new = array_combine(range(1, count($arr)), $arr);

The above code will create a new array $arr_new, whose index starts from 1.

It should be noted that the length of the array generated by the range function must be the same as the length of the original array. If the lengths of the two arrays do not correspond, a warning is generated. Furthermore, this approach only works with associative arrays. For ordinary indexed arrays, the array subscripts may be reordered.

Summary

It may be necessary to start the PHP array subscript from 1. Among the three methods, manually modifying the array subscript is the most intuitive and best-performing way; change Although the array pointer method is feasible, it is less efficient and has a limited scope of application; using the array_combine function is also a better method, but its scope of application is narrower and only applies to associative arrays. It is necessary to choose the appropriate method to meet the needs based on the actual situation.

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