Learn the conversion and judgment of PHP string encoding

This article introduces a piece of code for transcoding and judging string encoding in PHP programming. Friends in need can use it as a reference. It is often necessary to implement GBK and UTF-8 encoding conversion in PHP. For example, json_encode in PHP itself does not support GBK encoding at all. There are two library functions that can support encoding conversion. The one that usually comes to mind is the iconv function. For example:

<?php
iconv('GBK', 'UTF-8//IGNORE', '芒果小站'); // 将字符串由 GBK 编码转换为 UTF-8 编码

But iconv can only solve the situation where the encoding is known in advance. If the string encoding is unknown, you need to detect its encoding first. In this case, the mb_string extension library may be used:

<?php
mb_detect_encoding('程序员之家');

However, mb_detect_encoding has a flaw, and inaccurate judgment often occurs. You can refer to the following solutions:

<?php
// 使用 iconv 转换并判断是否等值，效率不高
function is_utf8 ($str) {
    if ($str === iconv('UTF-8', 'UTF-8//IGNORE', $str)) {
        return 'UTF-8';
    }
}
// 多种编码的情况
function detect_encoding ($str) {
    foreach (array('GBK', 'UTF-8') as $v) {
        if ($str === iconv($v, $v . '//IGNORE', $str)) {
            return $v;
        }
    }
}

After obtaining the string encoding information through the above method, you can use iconv or mb_convert_encoding to perform encoding conversion.