Let's talk in depth about the replacement element operation of PHP arrays

PHP is a widely used server-side scripting language. It has powerful data processing capabilities and flexibility and is widely used in Web development. Among them, array is a very important data type, often used to store and operate data. In PHP, we can use built-in functions to perform various operations on arrays, such as adding, deleting, querying, sorting, traversing, etc. This article will focus on the replacement element operation of PHP arrays and provide specific code examples.

1. Common functions for replacing array elements

PHP provides multiple functions for replacing elements in arrays, of which the following three functions are the most commonly used:

1. array_replace($array1, $array2)

This function replaces the elements in array 2 with the corresponding elements in array 1. If there are the same key names in array 1 or array 2, Then use the values ​​in the latter array to replace the values ​​in the previous array. Please look at the following code example:

$array1 = array('a' => 'apple', 'b' => 'banana', 'c' => 'cherry');
$array2 = array('a' => 'apricot', 'd' => 'date');
$result = array_replace($array1, $array2);
print_r($result);

Execute the above code, you will get the following output:

Array
(
    [a] => apricot
    [b] => banana
    [c] => cherry
    [d] => date
)

As you can see, the key-value pair in array 1 ('a'=>'apple ') has been replaced by the key-value pair ('a'=>'apricot') in array 2, and the new key-value pair ('d'=>'date') in array 2 has also been added in the final result array.

2. array_replace_recursive($array1, $array2)

This function is very similar to array_replace(), but it recursively replaces the elements in array 2 with those in array 1 corresponding element. If the value in array1 or array2 is an array, the key-value pairs in that value will also be replaced recursively. Please look at the following code example:

$array1 = array('a' => array('b' => 'blue', 'c' => 'cyan'), 'd' => 'black');
$array2 = array('a' => array('b' => 'brown', 'e' => 'emerald'));
$result = array_replace_recursive($array1, $array2);
print_r($result);

Execute the above code and you will get the following output:

Array
(
    [a] => Array
        (
            [b] => brown
            [c] => cyan
            [e] => emerald
        )

    [d] => black
)

As you can see, the key-value pair in array 1 ('a'=>array( 'b'=>'blue', 'c'=>'cyan')) has been replaced by the key-value pair in array 2 ('a'=>array('b'=>'brown', ' e'=>'emerald')). Moreover, the subarrays within the array are also replaced recursively.

3. array_splice($array, $offset, $length, $replacement)

This function is used to delete the element at the specified position in the array and insert a new one at that position. Elements. Specifically, the $offset parameter represents the starting index position of the element to be deleted/replaced, the $length parameter represents the number of elements to be deleted (0 if no elements are deleted), and the $replacement parameter represents the new element to be inserted. Please look at the following code example:

$array = array('red', 'green', 'blue', 'yellow');
array_splice($array, 1, 2, array('purple', 'orange'));
print_r($array);

Execute the above code and you will get the following output:

Array
(
    [0] => red
    [1] => purple
    [2] => orange
    [3] => yellow
)

You can see that the 2 elements starting from index 1 in the original array ('green', 'blue') has been removed and two new elements ('purple', 'orange') have been inserted at index 1.

2. Application examples

Now, let’s take a look at how to use the above function to replace elements in a PHP array based on specific application scenarios.

1. Application of replacement rules

Suppose we have an array in which the key names are the Chinese names of some plants and the key values ​​are their English names. Now, we want to replace the English names of some of these plants, such as "apple" with "orange" and "cherry" with "grape", leaving the rest unchanged. This can be achieved using the array_replace() function. Please look at the sample code below:

$plants = array('苹果' => 'apple', '香蕉' => 'banana', '樱桃' => 'cherry', '葡萄' => 'grape');
$rules = array('apple' => 'orange', 'cherry' => 'grape');
$newPlants = array_replace($plants, $rules);
print_r($newPlants);

Execute the above code and you will get the following output:

Array
(
    [苹果] => orange
    [香蕉] => banana
    [樱桃] => grape
    [葡萄] => grape
)

You can see that the key values ​​​​of "Apple" and "Cherry" have been separated. Replaced with "orange" and "grape" while leaving the rest of the key values ​​unchanged.

2. Application of Multidimensional Array

Suppose we have a multidimensional array, the key name is the name of some cities, and the key value is an associative array, which contains The city's population, industry and other information. Now, we want to add and subtract the population of certain cities and save the results back to the original array. This can be achieved using the array_replace_recursive() function. The code is as follows:

$cities = array(
    '北京市' => array('人口' => 2154, '产业' => '政治、文化、金融、科技'),
    '上海市' => array('人口' => 2424, '产业' => '金融、贸易、科技、文化'),
    '广州市' => array('人口' => 1500, '产业' => '商贸、制造、物流、金融')
);
$rules = array(
    '北京市' => array('人口' => -100),
    '广州市' => array('人口' => 200)
);
$newCities = array_replace_recursive($cities, $rules);
print_r($newCities);

Execute the above code and you will get the following output:

Array
(
    [北京市] => Array
        (
            [人口] => 2054
            [产业] => 政治、文化、金融、科技
        )

    [上海市] => Array
        (
            [人口] => 2424
            [产业] => 金融、贸易、科技、文化
        )

    [广州市] => Array
        (
            [人口] => 1700
            [产业] => 商贸、制造、物流、金融
        )
)

As you can see, the population of Beijing has decreased by 1 million, and the population of Guangzhou has decreased by 1 million. The population of Shanghai increased by 2 million, while the information of Shanghai remained the same.

3. Application of deleting specified elements

Suppose we have an array that stores the names and ages of several individuals. Now, we want to delete information for people who are 30 years or older. This can be achieved using the array_splice() function. The code is as follows:

$people = array(
    array('name' => '张三', 'age' => 25),
    array('name' => '李四', 'age' => 35),
    array('name' => '王五', 'age' => 28),
    array('name' => '赵六', 'age' => 42)
);
for ($i = count($people) - 1; $i >= 0; $i--) {
    if ($people[$i]['age'] >= 30) {
        array_splice($people, $i, 1);
    }
}
print_r($people);

Execute the above code and you will get the following output:

Array
(
    [0] => Array
        (
            [name] => 张三
            [age] => 25
        )

    [1] => Array
        (
            [name] => 王五
            [age] => 28
        )

)

You can see that the information of two people aged 30 or above has been were successfully deleted, while the information of two people younger than 30 years old remained unchanged.

3. Summary

In PHP, array is a very commonly used data structure. We can use various functions to add, delete, modify and check it. In this article, we introduce the replacement element operation of PHP arrays, focusing on the usage of the three functions array_replace(), array_replace_recursive() and array_splice(), and provide code examples based on specific application scenarios. I hope this article can help readers better understand and use the relevant knowledge of PHP arrays.

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