How to determine whether two arrays are the same in php

PHP is a widely used server-side scripting language that can be used in many fields such as dynamic websites, web application development, and command line interfaces. In PHP development, determining whether arrays are the same is a common problem. This article will introduce how to determine whether two arrays are the same in PHP.

In PHP, array is a very important data type used to store a set of values ​​or a set of key-value pairs. PHP can create arrays in a variety of ways, the most common methods are using array literals or using the array() function. For example:

$arr1 = [1, 2, 3];
$arr2 = array('a' => 1, 'b' => 2, 'c' => 3);

To determine whether two arrays are the same, we usually determine whether the elements they contain and the values ​​of the elements are the same. PHP provides a variety of methods to achieve this purpose, and their use is introduced below.

Method 1: Use the == operator

The == operator in PHP can be used to compare whether two arrays are equal. If two arrays contain the same elements but in a different order, the == operator will also consider them equal. For example:

$arr1 = [1, 2, 3];
$arr2 = [3, 2, 1];
if ($arr1 == $arr2) {
    echo "两个数组相等";
} else {
    echo "两个数组不相等";
}

The output of the above code is "the two arrays are equal" because $arr1 and $arr2 contain the same elements, that is, 1, 2, 3, but their order is different.

If the array contains nested arrays, the == operator only compares the references to the nested arrays rather than their values. For example:

$arr1 = [[1, 2], [3, 4]];
$arr2 = [[1, 2], [3, 4]];
if ($arr1 == $arr2) {
    echo "两个数组相等";
} else {
    echo "两个数组不相等";
}

The output result of the above code is "the two arrays are not equal" because $arr1 and $arr2 contain different nested arrays, namely [1, 2], [3, 4] and [ 1, 2], [3, 4].

Method 2: Use the === operator

Unlike the == operator, the === operator in PHP will also compare the types of the two arrays. If two arrays have the same elements and the same element values, and their types are also the same, then the === operator considers them equal. For example:

$arr1 = [1, 2, 3];
$arr2 = array(1, 2, 3);
if ($arr1 === $arr2) {
    echo "两个数组相等";
} else {
    echo "两个数组不相等";
}

The output of the above code is "the two arrays are not equal" because although $arr1 and $arr2 contain the same elements, they are of different types. $arr1 is an array literal, and $ arr2 is an array created using the array() function.

If the array contains nested arrays, the === operator will also compare the types and values ​​of the nested arrays. For example:

$arr1 = [[1, 2], [3, 4]];
$arr2 = [[1, 2], [3, 4]];
if ($arr1 === $arr2) {
    echo "两个数组相等";
} else {
    echo "两个数组不相等";
}

The output result of the above code is "the two arrays are not equal", and the reason is the same as the case in method one.

Method 3: Use array_diff function

Although the above method can determine whether two arrays are equal, due to the need to compare all elements, this method may be slower or memory intensive for large arrays. Taking up too much space. In this case, you can use PHP's array_diff function to compare arrays. This function is used to calculate the difference between two arrays, that is, the elements contained in one array but not in the other array. If the difference between two arrays is empty, they are equal. For example:

$arr1 = [1, 2, 3];
$arr2 = [3, 2, 1];
if (empty(array_diff($arr1, $arr2)) && empty(array_diff($arr2, $arr1))) {
    echo "两个数组相等";
} else {
    echo "两个数组不相等";
}

The output result of the above code is "two arrays are equal", the reason is the same as the case in method one.

If the array contains nested arrays, you can call the array_diff function recursively. For example:

$arr1 = [[1, 2], [3, 4]];
$arr2 = [[3, 4], [1, 2]];
if (empty(array_diff($arr1, $arr2)) && empty(array_diff($arr2, $arr1))) {
    echo "两个数组相等";
} else {
    echo "两个数组不相等";
}

function array_equal($arr1, $arr2) {
    if (count($arr1) != count($arr2)) {
        return false;
    }
    $d1 = array_diff($arr1, $arr2);
    $d2 = array_diff($arr2, $arr1);
    if (!empty($d1) || !empty($d2)) {
        return false;
    }
    foreach ($arr1 as $key => $value) {
        if (is_array($value) && is_array($arr2[$key])) {
            if (!array_equal($value, $arr2[$key])) {
                return false;
            }
        } else if ($value !== $arr2[$key]) {
            return false;
        }
    }
    return true;
}

The array_equal function in the above code can recursively compare two arrays. For the processing of nested arrays, it also calls the array_diff function to compare the difference sets.

This article introduces three methods in PHP to determine whether two arrays are equal, namely using the == operator, using the === operator and using the array_diff function. When we need to determine whether arrays are equal, we can choose one of these methods according to the specific situation.

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