(PHP 3>= 3.0.8, PHP 4 , PHP 5)
strip_tags -- Strip HTML and PHP tags from a string
Description
string 
strip_tags ( string str [, string allowable_tags])
     This function tries to return a string with all HTML and PHP tags
     stripped from a given str.  It uses
     the same tag stripping state machine as the
     fgetss() function.
    
     You can use the optional second parameter to specify tags which
     should not be stripped.
     
注: 
       allowable_tags was added in PHP 3.0.13
       and PHP 4.0b3. Since PHP 4.3.0, HTML comments are also stripped.
      
| 警告 | 
| 
         Because strip_tags() does not actually validate the
         HTML, partial, or broken tags can result in the removal of more
         text/data than expected.
        | 
     
| 例子 1. strip_tags() example | 
<?php$text = '
 <p>Test paragraph.</p>
 <!-- Comment -->
 Other text';
 
 echo strip_tags($text);
 
 echo "\n\n-------\n";
 
 // allow <p>
 echo strip_tags($text, '<p>');
 ?>
 | 
 
       The above example will output:
       | Test paragraph.
Other text
-------
<p>Test paragraph.</p>
Other text | 
 | 
    | 警告 | 
| 
      This function does not modify any attributes on the tags that you allow
      using allowable_tags, including the
      style and onmouseover attributes
      that a mischievous user may abuse when posting text that will be shown
      to other users.
      | 
     See also htmlspecialchars().