Introduction to the specific method of intercepting UTF-8 strings with PHP

Introduction to the specific method of intercepting UTF-8 strings with PHP_PHP tutorial

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Release： 2016-07-15 13:30:34

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We For the principle of utf-8, please see UTF-8 FAQ

UTF-8 encoded characters may consist of 1~3 bytes, the specific number It can be judged from the first byte. (Theoretically it may be longer, but here it is assumed that it does not exceed 3 bytes)
The first byte is greater than 224, it and the 2 bytes after it form a UTF-8 character
The first If a byte is greater than 192 and less than 224, it and the 1 byte after it form a UTF-8 character
. Otherwise, the first byte itself is an English character (including numbers and a small part of punctuation marks).

Code previously designed for a website (also the length interception function now used on the homepage)

Code example for PHP interception of utf-8 strings:

<ol class="dp-xml">
<li class="alt"><span><span class="tag"><</span><span> ?php // Cut_Str;  </span></span></li><li><span>//$sourcestr 是要处理的字符串  </span></li><li class="alt"><span>//$cutlength 为截取的长度(即字数)  </span></li><li><span>function cut_str($sourcestr,$cutlength)  </span></li><li class="alt"><span>{  </span></li><li><span>$</span><span class="attribute">returnstr</span><span>=&rdquo;;  </span></li><li class="alt"><span>$</span><span class="attribute">i</span><span>=</span><span class="attribute-value">0</span><span>;  </span></li><li><span>$</span><span class="attribute">n</span><span>=</span><span class="attribute-value">0</span><span>;  </span></li><li class="alt"><span>$</span><span class="attribute">str_length</span><span>=</span><span class="attribute-value">strlen</span><span>($sourcestr);//字符串的字节数  </span></li><li><span>while (($n</span><span class="tag"><</span><span>$cutlength) and ($i</span><span class="tag"><</span><span>=$str_length))  </span></li><li class="alt"><span>{  </span></li><li><span>$</span><span class="attribute">temp_str</span><span>=</span><span class="attribute-value">substr</span><span>($sourcestr,$i,1);  </span></li><li class="alt"><span>$</span><span class="attribute">ascnum</span><span>=</span><span class="attribute-value">Ord</span><span>($temp_str);//得到字符串中第$i位字符的ascii码  </span></li><li><span>if ($ascnum</span><span class="tag">></span><span>=224) //如果ASCII位高与224，  </span></span></li>
<li class="alt"><span>{  </span></li>
<li>
<span>$</span><span class="attribute">returnstr</span><span>=$returnstr.substr($sourcestr,$i,3); <br>//根据UTF-8编码规范，将3个连续的字符计为单个字符  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">i</span><span>=$i+3; //实际Byte计为3  </span>
</li>
<li><span>$n++; //字串长度计1  </span></li>
<li class="alt"><span>}  </span></li>
<li>
<span>elseif ($ascnum</span><span class="tag">></span><span>=192) //如果ASCII位高与192，  </span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>$</span><span class="attribute">returnstr</span><span>=$returnstr.substr($sourcestr,$i,2);<br> //根据UTF-8编码规范，将2个连续的字符计为单个字符  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">i</span><span>=$i+2; //实际Byte计为2  </span>
</li>
<li><span>$n++; //字串长度计1  </span></li>
<li class="alt"><span>}  </span></li>
<li>
<span>elseif ($ascnum</span><span class="tag">></span><span>=65 && $ascnum</span><span class="tag"><</span><span>=90) <br />//如果是大写字母，  </span></li><li class="alt"><span>{  </span></li><li><span>$</span><span class="attribute">returnstr</span><span>=$returnstr.substr($sourcestr,$i,1);  </span></li><li class="alt"><span>$</span><span class="attribute">i</span><span>=$i+1; //实际的Byte数仍计1个  </span></li><li><span>$n++; //但考虑整体美观，大写字母计成一个高位字符  </span></li><li class="alt"><span>}  </span></li><li><span>else //其他情况下，包括小写字母和半角标点符号，  </span></li><li class="alt"><span>{  </span></li><li><span>$</span><span class="attribute">returnstr</span><span>=$returnstr.substr($sourcestr,$i,1);  </span></li><li class="alt"><span>$</span><span class="attribute">i</span><span>=$i+1; //实际的Byte数计1个  </span></li><li><span>$</span><span class="attribute">n</span><span>=$n+0.5; //小写字母和半角标点等与半个高位字符宽&hellip;  </span></li><li class="alt"><span>}  </span></li><li><span>}  </span></li><li class="alt"><span>if ($str_length</span><span class="tag">></span><span>$cutlength){  </span>
</li>
<li>
<span>$</span><span class="attribute">returnstr</span><span> = $returnstr . “…”;<br>//超过长度时在尾处加上省略号  </span>
</li>
<li class="alt"><span>}  </span></li>
<li><span>return $returnstr;  </span></li>
<li class="alt"><span>} </span></li>
</ol>

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The above is a summary of the relevant methods of intercepting UTF-8 strings in PHP. I hope it will be helpful to everyone.