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

In PHP, array is a very common and important data type. Arrays can be divided into one-dimensional, two-dimensional and multi-dimensional forms. In this article, we will learn how to convert a 2D array into a 1D array.

One-dimensional array and two-dimensional array

In PHP, a one-dimensional array is an array with only one dimension. The elements can be any type of data, such as numbers, strings, objects, etc. .

For example:

$array1 = array("dog", "cat", "horse", "cow");

This array contains 4 elements, each element is string type data.

A two-dimensional array refers to an array containing two dimensions. The innermost elements of the array must be of the same data type.

For example:

$array2 = array(
   array("dog", "puppy"),
   array("cat", "kitten"),
   array("horse", "foal"),
   array("cow", "calf")
);

This two-dimensional array contains 4 elements, each element is a subarray containing 2 elements. Each subarray contains one element of type string and one element of type string.

How to convert a two-dimensional array into a one-dimensional array

When we need to process data, we often need to convert a two-dimensional array into a one-dimensional array. PHP provides a variety of methods to complete this task. The following are three methods:

Method 1: Use the "foreach" loop to traverse

First, we can use the foreach loop to traverse the two-dimensional array elements and then insert each element into a new one-dimensional array.

The following is the sample code:

$array2 = array(
   array("dog", "puppy"),
   array("cat", "kitten"),
   array("horse", "foal"),
   array("cow", "calf")
);

//创建一个新的一维数组
$array1 = array();

//遍历二维数组并插入一维数组中
foreach($array2 as $value) {
   foreach($value as $element) {
      array_push($array1, $element);
   }
}

//打印结果
print_r($array1);

In the above code, we use two foreach loops to iterate through the elements in the two-dimensional array and insert each element into the array. The final printed result is a one-dimensional array.

Method 2: Use the "array_reduce()" function

Another method is to use PHP's "array_reduce()" function, which can also convert a two-dimensional array into a one-dimensional array.

The following is a sample code:

$array2 = array(
   array("dog", "puppy"),
   array("cat", "kitten"),
   array("horse", "foal"),
   array("cow", "calf")
);

//调用array_reduce()函数
$array1 = array_reduce($array2, 'array_merge', array());

//打印结果
print_r($array1);

In the above code, we use PHP's "array_reduce()" function and pass it three parameters: $array2 represents the data that needs to be converted Two-dimensional array, 'array_merge' represents a callback function used to insert each sub-array into a one-dimensional array, array() represents a one-dimensional array with an initial value of empty. The result returned by the function is an array that has been converted into a one-dimensional array.

Method 3: Use the "array_walk_recursive()" function

The last method is to use the "array_walk_recursive()" function, which can help us traverse all the elements in the two-dimensional array, and then Each element is inserted into a new one-dimensional array.

The following is a sample code:

$array2 = array(
   array("dog", "puppy"),
   array("cat", "kitten"),
   array("horse", "foal"),
   array("cow", "calf")
);

//创建一个新的一维数组
$array1 = array();

//调用array_walk_recursive()函数
function convert($value, $key, &$array1) {
   array_push($array1, $value);
}
array_walk_recursive($array2, 'convert', $array1);

//打印结果
print_r($array1);

In the above code, we first create an empty array as the target one-dimensional array, and then call the "array_walk_recursive()" function to traverse the two-dimensional array. The first parameter of the function represents the array that needs to be traversed, the second parameter is a callback function, which is used to insert each element traversed into the one-dimensional array, and the third parameter is the target one-dimensional array. The return value of the function is void, so there is no need to assign the return result to a variable.

Summary

Through the above three methods, we can convert a two-dimensional array into a one-dimensional array more conveniently. It can be seen that in PHP, array is a very commonly used data type, and it is very important to master the relevant skills.

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