如何在PHP中使用array_reduce（）？

array_reduce() 函数用于将数组缩减为单个值，通过迭代应用回调函数实现，常用于求和、拼接字符串或构建复杂数据结构。

The array_reduce() function in PHP is used to reduce an array to a single value by applying a callback function iteratively. It's useful for summing values, concatenating strings, or building complex data structures from arrays.

Syntax

• $array: The input array to process
• $callback: Function called for each element
• $initial: Optional initial value (used as $carry on first iteration)

The callback function takes two parameters:

• $carry: Accumulated value (result of previous iteration or initial value)
• $item: Current array element being processed

Summing Array Values

A common use is summing numbers in an array:

If the array is empty and no initial value is provided, array_reduce() returns null.

Building Strings or Complex Structures

You can also use it to concatenate strings or build associative arrays:

Or transform data:

Key Points

• The callback must return the updated $carry value
• An initial value ensures consistent behavior with empty arrays
• The function does not modify the original array
• It processes elements in order from left to right

Basically, array_reduce() gives you a clean way to boil down array contents into one result using custom logic. It’s powerful once you get the pattern of accumulating values through iterations.

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