Detailed explanation of PHP 5.5 functions: How to use the array_column function to extract a certain column in a two-dimensional array

Detailed explanation of PHP 5.5 function: How to use the array_column function to extract a column in a two-dimensional array

In the PHP 5.5 version, the array_column function was introduced. It is a very practical function that can extract a column from a two-dimensional array. Extract a specified column of data. This comes in handy when working with large amounts of data, allowing us to quickly get the data we need.

The basic syntax of the array_column function is as follows:

array array_column(array $input, mixed $column_key [, mixed $index_key ]);

Parameter explanation:

• $input: The two-dimensional array to extract data.
• $column_key: The key name or index of the column to be extracted.
• $index_key (optional): The key name or index used as the key of the returned array.

Next, we will use a practical example to explain in detail how to use the array_column function.

Suppose we have a two-dimensional array $employees, representing information about the company's employees, such as employee name, age and salary. We want to extract the names of all employees from this 2D array.

First, we need to define the employee array:

$employees = array(
    array(
        '姓名' => '张三',
        '年龄' => 25,
        '薪水' => 10000
    ),
    array(
        '姓名' => '李四',
        '年龄' => 30,
        '薪水' => 15000
    ),
    array(
        '姓名' => '王五',
        '年龄' => 35,
        '薪水' => 20000
    )
);

Now, we can use the array_column function to extract the employee’s name column:

$names = array_column($employees, '姓名');

The $names array will contain all employees’ names The name can be printed out through the print_r function:

print_r($names);

The output result is as follows:

Array
(
    [0] => 张三
    [1] => 李四
    [2] => 王五
)

As you can see, we successfully extracted the employee's name column data from the two-dimensional array.

In addition to extracting data from a certain column, the array_column function also supports setting the key of the returned array through the third parameter $index_key. Below we demonstrate how to set the keys of the returned array.

Continuing to use the previous $employees array, we will use the employee's name as the key of the returned array:

$names = array_column($employees, '姓名', '年龄');

In this way, the $names array will have the employee's age as the key, with the employee name as value. The result can be printed out through the print_r function:

print_r($names);

The output result is as follows:

Array
(
    [25] => 张三
    [30] => 李四
    [35] => 王五
)

As you can see, the array returned now uses the employee's age as the key, and the corresponding value is the employee's name.

To summarize, the array_column function is a very practical function provided in PHP version 5.5. It can quickly extract data in a certain column from a two-dimensional array. We can extract data by specifying the key name or index, and we can also specify the key of the returned array by setting the third parameter. In this way, we can process large amounts of data more flexibly and extract the information we need.

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