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

In PHP programming, arrays are usually important tools used to store and process data. In some cases, we need to convert a two-dimensional array into a one-dimensional array to facilitate subsequent processing and use. This article will introduce how to use the PHP programming language to implement this function.

First, we need to define a two-dimensional array as an example. The following is a simple example:

$cars = array(
  array("Volvo",22,18),
  array("BMW",15,13),
  array("Saab",5,2),
  array("Land Rover",17,15)
);

The above array represents four cars, including car name, sales volume and inventory. Next, we will show several methods to convert a two-dimensional array into a one-dimensional array.

1. Using a foreach loop

We can use a foreach loop to traverse each element of a two-dimensional array and convert it into an element in a one-dimensional array. The following is the code implementation:

$flat_cars = array();
foreach($cars as $car) {
  foreach($car as $detail) {
    $flat_cars[] = $detail;
  }
}

In the above code, an empty array $flat_cars will be created. Through the foreach loop, each element $car in the two-dimensional array $cars is traversed and decomposed into a one-dimensional array $detail. Then, add the elements in $detail to the $flat_cars array. Finally, $flat_cars becomes a one-dimensional array, where each element corresponds to an element in the original two-dimensional array $cars.

2. Using the array_reduce function

PHP's array_reduce function can accumulate an array through the specified callback function and return the last accumulated result. We can use this function to convert a two-dimensional array into a one-dimensional array.

$flat_cars = array_reduce($cars, 'array_merge', array());

In the above code, first we call the array_reduce function, pass in the original array $cars, and specify a callback function 'array_merge' for cumulative calculation. The 'array_merge' function will be incorporated as a parameter into the array_reduce function. Finally, by specifying an empty array as the third parameter of the array_reduce function, the $cars array can be converted into a one-dimensional array $flat_cars.

3. Use the array_column function

The array_column function is a very practical function after PHP 5.5. It can extract the value of a specific column in the array and return a one-dimensional array. . We can use it to convert a two-dimensional array into a one-dimensional array.

$flat_cars = array_column($cars, null, 0);

In the above code, we call the array_column function, passing in the original array $cars and the second parameter is null. The first parameter $cars indicates that the array of specific columns needs to be extracted, while the second parameter null indicates that the entire row of data will be extracted. The last parameter 0 means that the first element of the specified column (i.e. car name) will be extracted and a one-dimensional array will be returned. This one-dimensional array contains all elements of the $cars two-dimensional array.

Summary

In PHP programming, converting a two-dimensional array into a one-dimensional array is an extremely common operation. In this article, we introduce three methods to achieve this function, using foreach loop, array_reduce function and array_column function. Each method has its applicable scenarios, advantages and disadvantages, and you need to choose according to the actual situation when using it.

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