Describe the difference between strlen and mb_strlen in PHP_PHP Tutorial

In PHP, strlen and mb_strlen are functions to find the length of a string, but for some beginners, if you don’t read The manual may not be clear about the difference.
The following uses examples to explain the difference between the two.

Look at the example first:

<ol class="dp-c">
<li class="alt"><span><span><?php  </span></span></li><li><span class="comment">//测试时文件的编码方式要是UTF8 </span><span> </span></li><li class="alt"><span class="vars">$str</span><span>=</span><span class="string">'中文a字1符'</span><span>;  </span></li><li><span class="func">echo</span><span> </span><span class="func">strlen</span><span>(</span><span class="vars">$str</span><span>).</span><span class="string">'<br>'</span><span>;</span><span class="comment">//14 </span><span> </span></span></li>
<li class="alt">
<span class="func">echo</span><span> mb_strlen(</span><span class="vars">$str</span><span>,</span><span class="string">'utf8'</span><span>).</span><span class="string">'<br>'</span><span>;</span><span class="comment">//6 </span><span> </span>
</li>
<li>
<span class="func">echo</span><span> mb_strlen(</span><span class="vars">$str</span><span>,</span><span class="string">'gbk'</span><span>).</span><span class="string">'<br>'</span><span>;</span><span class="comment">//8 </span><span> </span>
</li>
<li class="alt">
<span class="func">echo</span><span> mb_strlen(</span><span class="vars">$str</span><span>,</span><span class="string">'gb2312'</span><span>).</span><span class="string">'<br>'</span><span>;</span><span class="comment">//10 </span><span> </span>
</li>
<li><span>?> </span></li>
</ol>

Result analysis: When calculating strlen, a UTF8 Chinese character is treated as 3 lengths, so "Chinese a character 1 The length of "character" is 3*4+2=14. When calculating mb_strlen, if the internal code is selected as UTF8, a Chinese character will be calculated as a length of 1, so the length of "Chinese a character 1 character" is 6.

Using these two functions, you can jointly calculate the occupancy of a mixed Chinese and English string (the occupancy of a Chinese character is 2, and the occupancy of an English character is 1)

<ol class="dp-c"><li class="alt"><span><span class="func">echo</span><span> (</span><span class="func">strlen</span><span>(</span><span class="vars">$str</span><span>) + mb_strlen(</span><span class="vars">$str</span><span>,</span><span class="string">'UTF8'</span><span>)) / 2; </span></span></li></ol>

For example, the strlen($str) value of "Chinese a character 1 character" is 14, and the mb_strlen($str) value is 6, then you can calculate "Chinese a character 1 character" "The placeholder is 10.

<ol class="dp-c"><li class="alt"><span><span class="func">echo</span><span> mb_internal_encoding(); </span></span></li></ol>

PHP's built-in string length function strlen cannot handle Chinese strings correctly. It only gets the length of the string. The number of bytes occupied. For GB2312 Chinese encoding, the value obtained by strlen is twice the number of Chinese characters, while for UTF-8 encoded Chinese, the difference is three times (under UTF-8 encoding, one Chinese character occupies 3 bytes).

Using the mb_strlen function can better solve this problem. The usage of mb_strlen is similar to strlen, except that it has a second optional parameter to specify the character encoding. For example, to get the UTF-8 string $str length, you can use mb_strlen($str,'UTF-8'). If the second parameter is omitted, PHP's internal encoding will be used. The internal encoding can be obtained through the mb_internal_encoding() function.

It should be noted that 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 is not commented out. , otherwise the problem of undefined function will occur.