What to do if php string lengths are inconsistent

Question:

As shown in the picture, at first glance there are two identical Chinese character strings "Logistics Support Department", but One has a length of 21 and one has a length of 15.

First of all, you may intuitively think that it is caused by different encoding methods.
Use the mb_detect_encoding() function to check the encoding methods of the two strings. The code is as follows

";
echo "str2='".$str2."'"." 编码:".$encode2."
";
?>

But the output results are all UTF-8

So what is the reason? Let’s check the specific character length in the output

";
echo "str2='".$str2."'".": 字符长度:".mb_strlen($str2).": 字节长度:".strlen($str2)." 编码:".$encode2."
";
?>

The output results are as follows:

It was found that the string str1 has 7 Chinese characters, but only 5 are actually displayed, which is the "Logistics Support Department"

By intercepting the last two characters of str1 Character view

//截取str1后面两个未显示字符
$res=mb_substr($str1, 5,2);
echo "最后两字符:".$res."
";
echo mb_strlen($res);

cannot be echo displayed, but it does occupy two characters

If the strings that look the same are actually required to be equal, processing needs to be performed. The processing is to eliminate non-Chinese characters:

//剔除str1字串中未显示的字符（非中文字符）
preg_match_all('/[\x{4e00}-\x{9fff}]+/u', $str1, $matches);
$str1 = join('', $matches[0]);

The final code is as follows

";
echo "str2='".$str2."'".": 字符长度:".mb_strlen($str2).": 字节长度:".strlen($str2)." 编码:".$encode2."
";

//截取str1后面两个未显示字符
echo "
------------------截取str1后面两个未显示字符---------------------
";
$res=mb_substr($str1, 5,2);
echo "str1最后两字符: ".$res."
";
echo "str1长度: ".mb_strlen($res)."
";

//比较
echo "
--------------------------相等比较----------------------------------
";
echo "str1 与 str2比较: ";
echo strcomp($str1,$str2)."
";
echo "str2 与 str2比较: ";
echo strcomp($str2,$str2)."
";


//剔除str1字串中非中文
preg_match_all('/[\x{4e00}-\x{9fff}]+/u', $str1, $matches);
$str1 = join('', $matches[0]);

echo "
---------------------剔除str1字串中非中文后----------------------
";
echo "str1='".$str1."'".": 字符长度:".mb_strlen($str1).": 字节长度:".strlen($str1)." 编码:".$encode1."
";
echo "str1 与 str2比较: ";
echo strcomp($str1,$str2)."
";

function strcomp($str1,$str2){ 
  if($str1 == $str2){ 
    return "相等"; 
  }else{ 
    return "不等"; 
  } 
} 

?>

Running results

##Note: Copy the 21-byte str1 to The sql input box of phpmyadmin displays as follows

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