PHP query returns a two-dimensional array

In PHP, we can use a variety of methods to query elements in an array, such as using the in_array() function, using the array_search() function, etc. But when we need to query elements in a two-dimensional array, these methods are less effective. This article will introduce how to query a two-dimensional array in PHP and return the required elements.

First, let us look at a simple two-dimensional array:

$students = array(
    array('name' => 'Tom', 'age' => 20, 'score' => 90),
    array('name' => 'Jack', 'age' => 22, 'score' => 85),
    array('name' => 'Mary', 'age' => 21, 'score' => 92),
);

Suppose we want to query the grades of a certain student, we can use foreach to loop through the array and use conditional statements to Determine whether they are the students we need, for example:

$wantedStudent = 'Jack';

foreach ($students as $student) {
    if ($student['name'] == $wantedStudent) {
        echo $wantedStudent . '的成绩是：' . $student['score'];
        break;
    }
}

The above code will output:

Jack的成绩是：85

However, if we need to query many students, this method will become very cumbersome. Therefore, we can encapsulate it into a function for use:

function searchArray($array, $key, $value) {
    foreach ($array as $item) {
        if ($item[$key] == $value) {
            return $item;
        }
    }
    return null;
}

The above function receives three parameters: array, key name and key value to be queried. It will iterate through the array and if it finds a match, it returns that item, otherwise it returns null.

We can use the function like this:

$wantedStudent = 'Mary';
$student = searchArray($students, 'name', $wantedStudent);

if ($student) {
    echo $wantedStudent . '的成绩是：' . $student['score'];
}

The above code is equivalent to the previous example and will output:

Mary的成绩是：92

However, when the array is very large, Iterating over the entire array will impact performance. Therefore, we can use the array function array_filter(), which takes an array and a callback function and returns a new array containing the array elements that meet the callback function's conditions.

The following is an example of using array_filter() to query a two-dimensional array:

function searchArray($array, $key, $value) {
    $filtered = array_filter($array, function($item) use ($key, $value) {
        return $item[$key] == $value;
    });
    return count($filtered) ? array_values($filtered)[0] : null;
}

The function of the above function is the same as the previous function, but it uses array_filter() to filter the conditions. array elements, thereby improving performance.

So far, we have learned how to query a two-dimensional array in PHP and return the required elements. It is recommended to use array_filter() and anonymous functions to implement array element query when there are hundreds or more pieces of data.

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