How to convert two-dimensional array to one-dimensional array in php

In PHP language, two-dimensional array is a very common data type. It consists of multiple one-dimensional arrays, each one-dimensional array has its own index value. Sometimes, we need to convert a two-dimensional array into a one-dimensional array for more convenient operations.

In this article, we will explore how to convert a two-dimensional array to a one-dimensional array using PHP and provide some sample code for your reference.

We will first look at what two-dimensional arrays are and why we need to convert them to one-dimensional arrays.

What is a two-dimensional array?

Simply put, a two-dimensional array in PHP is an array, and the elements of this array are one-dimensional arrays. In object-oriented programming, a two-dimensional array can also be called an array of arrays.

A two-dimensional array is composed of multiple one-dimensional arrays, and each one-dimensional array has its own index value. Generally, the index value of a two-dimensional array can be a number or a string, but the one-dimensional index value of a two-dimensional array must be a number, otherwise an error will occur.

Why do we need to convert a two-dimensional array to a one-dimensional array?

When processing some data, it is usually necessary to convert a two-dimensional array into a one-dimensional array. This makes it easier to operate on the data. Suppose you have a 2D array that stores student scores. You may want to get the total score of all students, or you may only want to query the results of a specific student, etc. In these cases, converting the array to a one-dimensional array can make it easier to find the data you need.

Method 1: Use a foreach loop

The simplest method is to use a foreach loop to traverse the array and add all elements to a new one-dimensional array.

Sample code:

// 假设我们有一个二维数组
$two_dimensional_array = array(
    array('id' => 1, 'name' => 'Tom', 'age' => 20),
    array('id' => 2, 'name' => 'Kate', 'age' => 25),
    array('id' => 3, 'name' => 'Bob', 'age' => 30),
);

// 创建一个新的一维数组
$one_dimensional_array = array();

// 循环遍历二维数组
foreach($two_dimensional_array as $key => $value) {
    // 循环遍历一维数组，将值添加到新的一维数组中
    foreach($value as $k => $v) {
        $one_dimensional_array[] = $v;
    }
}

// 打印一维数组
print_r($one_dimensional_array);

Output:

Array
(

[0] => 1
[1] => Tom
[2] => 20
[3] => 2
[4] => Kate
[5] => 25
[6] => 3
[7] => Bob
[8] => 30

)

Method 2: Use array_reduce function

The array_reduce function in PHP can use a function to iteratively combine an array into a single value. The first parameter of this function is an array, and the second parameter is a callback function.

The callback function requires two parameters, an accumulator and a current value. It adds the accumulator and the current value and returns the result. The return value of the array_reduce function is the final accumulator value.

In this example, we used the array_merge function to merge all the values ​​into an array.

Sample code:

// 假设我们有一个二维数组
$two_dimensional_array = array(
    array('id' => 1, 'name' => 'Tom', 'age' => 20),
    array('id' => 2, 'name' => 'Kate', 'age' => 25),
    array('id' => 3, 'name' => 'Bob', 'age' => 30),
);

// 使用array_reduce函数将二维数组转换为一维数组
$one_dimensional_array = array_reduce($two_dimensional_array, 'array_merge', array());

// 打印一维数组
print_r($one_dimensional_array);

Output:

Array
(

[id] => 3
[name] => Bob
[age] => 30

)

As you can see, array_reduce function Only the data of the last array is returned.

Method 3: Use the array_column function

Another method to convert a two-dimensional array to a one-dimensional array is to use the array_column function. This function returns a specified array column by the specified key.

Sample code:

// 假设我们有一个二维数组
$two_dimensional_array = array(
    array('id' => 1, 'name' => 'Tom', 'age' => 20),
    array('id' => 2, 'name' => 'Kate', 'age' => 25),
    array('id' => 3, 'name' => 'Bob', 'age' => 30),
);

// 使用array_column函数将二维数组转换为一维数组
$one_dimensional_array = array_column($two_dimensional_array, 'name');

// 打印一维数组
print_r($one_dimensional_array);

Output:

Array
(

[0] => Tom
[1] => Kate
[2] => Bob

)

You can specify different keys by to return different array columns.

Summary:

In PHP, there are many ways to convert a two-dimensional array into a one-dimensional array. Using a foreach loop to iterate through an array is the most common method. You can also use the array_reduce function or array_column function to achieve conversion.

The converted one-dimensional array can be more conveniently operated and queried. Converting a two-dimensional array to a one-dimensional array is a very useful technique if you need to handle complex multi-dimensional arrays in PHP.

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