Using PHP get_headers() to Retrieve HTTP Response Headers

Overview: In PHP development, the get_headers() function conveniently obtains the response header information of a target URL and returns it as an array.

Function usage: get_headers() can retrieve the response headers of a specified URL and return them in array form. The basic syntax is:

array get_headers(string $url, int $format = 0)

The $url parameter specifies the target URL. The optional $format parameter determines the format of the returned array: 0 (default) returns an associative array with indexes and values, while 1 returns an indexed array.

Code example:

$url = "https://www.example.com";

$headers = get_headers($url);

// Print all response header information
print_r($headers);

// Print specific header lines
echo $headers[0]; // First header line
echo $headers[1]; // Second header line

Output example:

Array (
    [0] => HTTP/1.1 200 OK
    [1] => Date: Thu, 19 Nov 2020 08:00:00 GMT
    [2] => Server: Apache/2.4.41
    [3] => Content-Type: text/html; charset=UTF-8
    [4] => Content-Length: 12345
    ...
)

Application scenarios for get_headers() include:

Obtaining remote file information such as size and MIME type.

Checking whether a remote file exists by examining HTTP status codes.

Web crawling and network monitoring, where header data helps decide further processing.

Note: get_headers() works only with the HTTP protocol and is not applicable to other protocols like FTP.

Summary: The get_headers() function is a practical PHP tool for retrieving various HTTP header details—including status codes, dates, server info, and file size—enhancing code usability and efficiency when used appropriately in backend development.