Comparison of strlen() and mb_strlen() in PHP

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First take a look at what the official documentation says;

strlen()-used to get the string length

##int strlen ( string $ string )

Returns the length of the given string string.

mb_strlen — Get the length of the string

##mixed mb_strlen ( string $str[, string $encoding = mb_internal_encoding() ] )

string.

str: ​​The string to check the length of.

encoding: The encoding parameter is the character encoding. If omitted, the internal character encoding is used.

Note: The strlen() function cannot correctly handle Chinese strings. It only gets the number of bytes occupied by the string.

In strlen(), the encoding is GB2312, and one Chinese character occupies 2 bytes. If encoded as utf-8, one Chinese character occupies 3 bytes.

However,

In mb_strlen(), if the encoding is utf-8, the length of a Chinese character output is 1. Code to help understand:

<?php
	header("Content-type:text/html;charset=utf-8");
	
	echo "关于字符串你长度获取的测试"."<br />";
	
	$_str_y = "hello";
	$_str_c = "你好";
	
	//strlen()
	echo "strlen()输出hello的长度".strlen($_str_y)."<br />";
	echo "strlen()输出&#39;你好&#39;的长度".strlen($_str_c)."<br />";
	/**
	 * 输出：
	 * strlen()输出hello的长度5
	 * strlen()输出&#39;你好&#39;的长度6
	 */
	
	//mb_strlen()
	echo "mb_strlen( 不指定字符编码 )输出hello的长度".mb_strlen($_str_y)."<br />";
	echo "mb_strlen( 不指定字符编码 )输出&#39;你好&#39;的长度".mb_strlen($_str_c)."<br />";	
	/**
	 * mb_strlen( 不指定字符编码 )输出hello的长度5
	 * mb_strlen( 不指定字符编码 )输出&#39;你好&#39;的长度6
	 */
	
	//mb_strlen()
	echo "mb_strlen( utf-8 )输出hello的长度".mb_strlen($_str_y,&#39;utf-8&#39;)."<br />";
	echo "mb_strlen( utf-8 )输出&#39;你好&#39;的长度".mb_strlen($_str_c,&#39;utf-8&#39;)."<br />";
	
	/**
	 * 输出：
	 * mb_strlen( utf-8 )输出hello的长度5
	 * mb_strlen( utf-8 )输出&#39;你好&#39;的长度2
	 */
	
	
?>

Note: mb_strlen is not a core function of PHP. Before using it, you need to make sure that php_mbstring.dll is loaded in php.ini, that is, make sure that the line "extension=php_mbstring.dll" exists. And it is not commented out, otherwise the problem of undefined function will occur.

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