php去除html标识截取字符串

最近需要在HTML的内容中提取一段文本作为简介，如果用普通的办法提取那么将有可能出现截取了半个HTML标志的情况，会破坏页面布局， 为此添加了这么一个函数，可完美解决此问题！！注意在这里你截取的字符数是不含HTML标志的！！

1. <?php   
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2. /**  
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3. * 截取HTML字符串 允许忽略HTML标志不计  
   
4. *  
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5. * Author：学无止境  
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6. * Email：xjtdy888@163.com  
   
7. * QQ: 339534039  
   
8. * Home:http://www.phpos.org  
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9. * Blog:http://hi.baidu.com/phps  
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10. *  
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11. * 转载请保留作者信息  
    
12. 
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13. *   
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14. * @param 要截取的HTML $str  
    
15. * @param 截取的数量 $num  
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16. * @param 是否需要加上更多 $more  
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17. * @return 截取串  
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18. */  
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19. function phpos_chsubstr_ahtml($str,$num,$more=false)   
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20. {   
    
21.     $leng=strlen($str);   
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22.       if($num>=$leng)      return $str;   
    
23.     $word=0;   
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24.     $i=0;                        /** 字符串指针 **/  
    
25.     $stag=array(array());        /** 存放开始HTML的标志 **/  
    
26.     $etag=array(array());        /** 存放结束HTML的标志 **/  
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27.     $sp = 0;   
    
28.     $ep = 0;   
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29.       while($word!=$num)   
    
30.       {   
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31.   
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32.           if(ord($str[$i])>128)   
    
33.           {   
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34.             //$re.=substr($str,$i,3);   
    
35.             $i+=3;   
    
36.             $word++;   
    
37.           }   
    
38.           else if ($str[$i]=='<')   
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39.           {   
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40.               if ($str[$i+1] == '!')   
    
41.               {   
    
42.                 $i++;   
    
43.                   continue;   
    
44.               }   
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45.   
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46.               if ($str[$i+1]=='/')      
    
47.               {   
    
48.                 $ptag=$etag ;   
    
49.                 $k=$ep;   
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50.                 $i+=2;   
    
51.               }   
    
52.               else                       
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53.               {   
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54.                 $ptag=$stag;   
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55.                 $i+=1;   
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56.                 $k=$sp;   
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57.               }   
    
58.   
    
59.               for(;$i<$leng;$i++)           
    
60.               {   
    
61.                   if ($str[$i] == ' ')   
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62.                   {   
    
63.                     $ptag[$k] = implode('',$ptag[$k]);   
    
64.                     $k++;   
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65.                       break;   
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66.                   }   
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67.                   if ($str[$i] != '>')   
    
68.                   {   
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69.                     $ptag[$k][]=$str[$i];   
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70.                       continue;   
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71.                   }   
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72.                   else                  
    
73.                   {   
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74.                     $ptag[$k] = implode('',$ptag[$k]);   
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75.                     $k++;   
    
76.                       break;   
    
77.                   }   
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78.               }   
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79.             $i++;   
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80.               continue;   
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81.           }   
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82.           else  
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83.           {   
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84.             //$re.=substr($str,$i,1);   
    
85.             $word++;   
    
86.             $i++;   
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87.           }   
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88.       }   
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89.       foreach ($etag as $val)   
    
90.       {   
    
91.         $key1=array_search($val,$stag);   
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92.           if ($key1 !== false)          unset($stag[$key]);   
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93.       }   
    
94.       foreach ($stag as $key => $val)   
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95.       {   
    
96.           if (in_array($val,array('br','img'))) unset($stag[$key1]);   
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97.       }   
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98.     array_reverse($stag);   
    
99.     $ends = '</'.implode('></',$stag).'>';   
    
100.     $re = substr($str,0,$i).$ends;   
     
101.       if($more)    $re.='...';   
     
102.       return $re;   
     
103. }   
     
104.   
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105. $str=<<<EOF   
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106. <h3>What is the <acronym>GNU</acronym> pr<a><a><a>oject?</h3>   
     
107. <p>The <acronym>GNU</acronym> Project was launched in 1984 to develop a complete Unix-like operating system which is <a href="http://www.gnu.org/philosophy/free-sw.html">free software</a>: the <acronym>GNU</acronym> system. Variants of the <acronym>GNU</acronym> operating system, which use the kernel called Linux, are now widely used; though these systems are often referred to as “Linux”, they are more accurately called <a href="http://www.gnu.org/gnu/linux-and-gnu.html">GNU/Linux systems</a>. </p>   
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108. <p><acronym>GNU</acronym> is a recursive acronym for “GNU's Not Unix”; it is pronounced <em>guh-noo</em>, approximately like <em>canoe</em>.</p>  
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109. <h3>What is Free Software?</h3>  
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110. <p>“<a href="http://www.gnu.org/philosophy/free-sw.html">Free software</a>” is a matter of liberty, not price. To understand the concept, you should think of “free” as in “free speech”, not as in “free beer”.</p>  
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111. <p>Free software is a matter of the users' freedom to run, copy, distribute, study, change and improve the software. More precisely, it refers to four kinds of freedom, for the users of the software:</p>   
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112. <ul>   
     
113.       <li>The freedom to run the program, for any purpose (freedom 0). </li>   
     
114.       <li>The freedom to study how the program works, and adapt it to your needs (freedom 1). Access to the source code is a precondition for this. </li>   
     
115.       <li>The freedom to redistribute copies so you can help your neighbor (freedom 2). </li>   
     
116.       <li>The freedom to improve the program, and release your improvements to the public, so that the whole community benefits (freedom 3). Access to the source code is a precondition for this. </li>   
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117. </ul>   
     
118. <h3>What is the Free Software Foundation?</h3>   
     
119. <p>The <a href="http://www.fsf.org/">Free Software Foundation</a> (<abbr title="Free Software Foundation">) is the principal organizational sponsor of the Project. The receives very little funding from corporations or grant-making foundations, but relies on support from individuals like you. </abbr>) is the principal organizational sponsor of the Project. The receives very little funding from corporations or grant-making foundations, but relies on support from individuals like you. </p>   
     
120. <p>Please consider helping the <abbr>by , or by . If you use Free Software in your business, you can also consider or as a way to support the . </abbr>by , or by . If you use Free Software in your business, you can also consider or as a way to support the . </p>   
     
121. <p>The <acronym>GNU</acronym> project supports the mission of the <abbr>to preserve, protect and promote the freedom to use, study, copy, modify, and redistribute computer software, and to defend the rights of Free Software users. We support the on the Internet, , and the unimpeded by private monopolies. You can also learn more about these issues in the book . </abbr>to preserve, protect and promote the freedom to use, study, copy, modify, and redistribute computer software, and to defend the rights of Free Software users. We support the on the Internet, , and the unimpeded by private monopolies. You can also learn more about these issues in the book . </p>   
     
122. <!--   
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123. Keep link lines at 72 characters or lynx will break them poorly   
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124. Obviously, we list ONLY the most useful/important URLs here   
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125. Keep it short and sweet: 3 lines and 2 columns is already enough   
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126. --><!-- BEGIN GNUmenu -->   
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127. EOF;   
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128. echo phpos_chsubstr_ahtml($str,800);   
     
129. ?>   
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