preg_quote
    (PHP 3 >= 3.0.9, PHP 4, PHP 5)
preg_quote -- Quote regular expression characters
Description
string 
preg_quote ( string str [, string delimiter] )
   preg_quote() takes str
   and puts a backslash in front of every character that is part of
   the regular expression syntax.  This is useful if you have a
   run-time string that you need to match in some text and the
   string may contain special regex characters.
  
   The special regular expression characters are:
   . \ + * ? [ ^ ] $ ( ) { } = ! < > | :
  
Parameters
   
str
       The input string.
      
delimiter
       If the optional delimiter is specified, it
       will also be escaped.  This is useful for escaping the delimiter
       that is required by the PCRE functions. The / is the most commonly
       used delimiter.
      
 
  Return Values
   Returns the quoted string.
  
Examples
   
Example 1. preg_quote() example 
<?php $keywords = '$40 for a g3/400'; $keywords = preg_quote($keywords, '/'); echo $keywords; // returns \$40 for a g3\/400 ?>
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Example 2. Italicizing a word within some text 
<?php // In this example, preg_quote($word) is used to keep the // asterisks from having special meaning to the regular // expression.
  $textbody = "This book is *very* difficult to find."; $word = "*very*"; $textbody = preg_replace ("/" . preg_quote($word) . "/",                           "<i>" . $word . "</i>",                           $textbody); ?>
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  Notes
Note: This function is
binary-safe.