php two-dimensional array to one-dimensional array

In PHP, an array is a very powerful and flexible data structure that can store many different types of data. PHP arrays can be single-dimensional arrays, two-dimensional arrays, multi-dimensional arrays, etc.

In the actual development process, we often need to convert a two-dimensional array into a one-dimensional array to make it easier to traverse and process data. This article will introduce how to convert a two-dimensional array into a one-dimensional array in PHP.

PHP two-dimensional array

In PHP, a two-dimensional array is an array in which the elements in the array are also arrays. For example:

$students = array(
    array("name" => "John", "age" => 23, "score" => 90),
    array("name" => "Mike", "age" => 21, "score" => 80),
    array("name" => "Mary", "age" => 22, "score" => 85)
);

Here we create a $students array, which contains three elements, each element is an array, containing the student's name, age and grades.

Convert a two-dimensional array to a one-dimensional array

In PHP, there are many ways to convert a two-dimensional array to a one-dimensional array. Here are several commonly used methods:

Method 1: Loop traversal

We can loop through each element of the two-dimensional array and then merge it into a new one-dimensional array. .

$students = array(
    array("name" => "John", "age" => 23, "score" => 90),
    array("name" => "Mike", "age" => 21, "score" => 80),
    array("name" => "Mary", "age" => 22, "score" => 85)
);

$newArray = array();
foreach ($students as $student) {
    foreach ($student as $key => $value) {
        $newArray[$key][] = $value;
    }
}

print_r($newArray);

The output result of the above code is:

Array
(
    [name] => Array
        (
            [0] => John
            [1] => Mike
            [2] => Mary
        )

    [age] => Array
        (
            [0] => 23
            [1] => 21
            [2] => 22
        )

    [score] => Array
        (
            [0] => 90
            [1] => 80
            [2] => 85
        )

)

As you can see, through loop traversal, we convert the two-dimensional array into a new associative array, each element of which corresponds to the original A key value for each element of the two-dimensional array.

Method 2: Use the array_column function

PHP provides the array_column function to obtain specified columns from a multi-dimensional array. We can use this function to get the name, age, and score of each student and then merge them into a new one-dimensional array.

$students = array(
    array("name" => "John", "age" => 23, "score" => 90),
    array("name" => "Mike", "age" => 21, "score" => 80),
    array("name" => "Mary", "age" => 22, "score" => 85)
);

$newArray = array(
    "name" => array_column($students, "name"),
    "age" => array_column($students, "age"),
    "score" => array_column($students, "score")
);

print_r($newArray);

The output result of the above code is the same as method one.

Method 3: Using the array_reduce function

We can use the array_reduce function to iterate over two-dimensional arrays and then merge them into a new one-dimensional array.

$students = array(
    array("name" => "John", "age" => 23, "score" => 90),
    array("name" => "Mike", "age" => 21, "score" => 80),
    array("name" => "Mary", "age" => 22, "score" => 85)
);

$newArray = array_reduce($students, function($carry, $student) {
    foreach ($student as $key => $value) {
        $carry[$key][] = $value;
    }
    return $carry;
}, array());

print_r($newArray);

The output result of the above code is the same as method one.

Method 4: Custom function

We can also customize a function to convert a two-dimensional array into a one-dimensional array.

function array_convert($arr) {
    $result = array();
    foreach ($arr as $row) {
        foreach ($row as $key => $value) {
            $result[$key][] = $value;
        }
    }
    return $result;
}

$students = array(
    array("name" => "John", "age" => 23, "score" => 90),
    array("name" => "Mike", "age" => 21, "score" => 80),
    array("name" => "Mary", "age" => 22, "score" => 85)
);

$newArray = array_convert($students);
print_r($newArray);

The output result of the above code is the same as method one.

Summary

In PHP, there are many ways to convert a two-dimensional array into a one-dimensional array, including loop traversal, using the array_column function, using the array_reduce function, and custom functions. Which method to choose depends on the needs of the specific scenario and development habits. In the actual development process, we need to use these methods flexibly in order to process data more efficiently.

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