array_reduce 函數(shù)通過(guò)迭代應(yīng)用回調(diào)函數(shù)將數(shù)組簡(jiǎn)化為單個(gè)值，常用于求和、拼接字符串或轉(zhuǎn)換數(shù)據(jù)結(jié)構(gòu)。1. 語(yǔ)法為 array_reduce($array, $callback, $initial)，$callback 接收 $carry（累積值）和 $item（當(dāng)前元素）。2. 求和示例：$numbers = [1,2,3,4,5]，經(jīng)回調(diào)累加后結(jié)果為 15。3. 字符串拼接：以 "Fruits: " 為初始值，逐個(gè)添加元素，得 "Fruits: , apple, banana, cherry"。4. 數(shù)據(jù)結(jié)構(gòu)轉(zhuǎn)換：將用戶數(shù)組轉(zhuǎn)為 ID 映射名稱(chēng)的關(guān)聯(lián)數(shù)組，初始值為空數(shù)組，結(jié)果為 [1=>'Alice',2=>'Bob']。若數(shù)組為空且無(wú)初始值，返回 null；回調(diào)應(yīng)始終返回 $carry 以確保正確累積。

The array_reduce function in PHP is used to reduce an array to a single value by applying a callback function iteratively. It processes each element of the array and accumulates a result based on your logic. This is useful for tasks like summing values, concatenating strings, or building complex data structures from arrays.

Basic Syntax

The function signature is:

• $array: The input array to process
• $callback: A function that takes two parameters (carry and item) and returns a new carry value
• $initial: Optional starting value for the carry

Summing Array Values

A common use is adding up numbers in an array.

Here, $carry holds the running total, and $item is each array element.

Building Strings or Custom Output

You can use it to concatenate strings with formatting.

Note the initial value sets the starting string. You might need to adjust formatting for cleaner output.

Transforming Data Structures

It's also powerful for converting arrays into associative formats.

This builds a map of user IDs to names, starting with an empty array as the initial value.

Basically just pass your array and a function that updates the accumulator. If the array is empty and no initial value is given, array_reduce returns null. Make sure your callback always return the carry unless you have a special case.

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