How to transpose a two-dimensional object array in php

In PHP, the most common two-dimensional array is a two-dimensional associative array stored in the form of key-value pairs, for example:

$students = array(
    array('name' => 'Alice', 'score' => 85),
    array('name' => 'Bob', 'score' => 72),
    array('name' => 'Charlie', 'score' => 91)
);

As shown above, $studentsThe array uses To store students' names and grades, where each element is an associative array. In some scenarios, we may need to transpose the data, that is, convert the data in each column into one row, and convert the data in each row into one column. For example, after transposing the above array, the result should be:

$transposed = array(
    array('name' => 'Alice', 'Bob', 'Charlie'),
    array('score' => 85, 72, 91)
);

Such an array structure is more suitable for certain analysis and statistical operations. This article will introduce how to use PHP to transpose a two-dimensional associative array.

Method 1: Use foreach loop to transpose

The simplest method is to use foreach loop to traverse the original array and generate a new array. The specific implementation is as follows:

function array_transpose($array) {
    $result = array();
    foreach ($array as $key => $row) {
        foreach ($row as $subkey => $subvalue) {
            $result[$subkey][$key] = $subvalue;
        }
    }
    return $result;
}

This function accepts a two-dimensional associative array as a parameter and returns the transposed new array. First, we define an empty array $result as the result array. We then use a double loop to iterate through the original array, turning rows into columns and columns into rows. In the inner loop, we use $subkey as the key of the new array and assign the value $subvalue in the original array to the value of the new array. In the outer loop, we use $key as the column name of the new array, and add the new column to the $result array. Finally, the new transposed array is returned.

Using this function, we can easily transpose the above example array:

$transposed = array_transpose($students);

The advantage of using this method is that it is simple and easy to understand and suitable for small-scale data. The disadvantage is that Performance is poor when the amount of data is large.

Method 2: Use array_map and call_user_func_array functions to transpose

Another method is to use the array_map and call_user_func_array functions provided by PHP. The implementation of this method is simpler and more efficient. The specific implementation is as follows:

function array_transpose($array) {
    return call_user_func_array('array_map', array_merge(array(null), $array));
}

This function also accepts a two-dimensional associative array as a parameter and returns the new array after transposition. First, we use the array_merge function to merge the $array array with a null value and pass it to the call_user_func_array function. In this example, the array_map function handles the merged arrays. The first parameter of the array_map function is a callback function that specifies how each input array position should be treated. A null value indicates that the callback function has no parameter name and uses default values ​​to process the input array. In our example, the callback function will list all input array index positions as rows, using $array to create a column. This is extremely important to help transform the behavior of this data, in fact this function will accept the first value of each array as an argument and replace it with the array itself. Since each key appears only once in the array, the resulting array is guaranteed to be free of conflicts.

Using this function, we can transpose the above example array as follows:

$transposed = array_transpose($students);

The advantages of this method are that it is efficient, concise and easy to understand, and is suitable for large-scale data and complex operations.

Summary

There are two ways to implement the two-dimensional associative array transposition operation in PHP: using a foreach loop and using the array_map and call_user_func_array functions. Both methods have their own advantages, and which method to choose depends on the specific application scenario. For small-scale data volumes, you can choose the foreach loop method. For large-scale data volumes and complex operations, it is recommended to use the array_map and call_user_func_array function methods.

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