尝试以下操作：

 function guru20_ReplaceWords($text){
 $replace = array(\'WordPress Codex\' =&gt; \'<a href="http:/codex.wordpress.com">WordPress Codex [EN]</a>\',
             \'WPRecipes\'=&gt; \'<a href="http://www.wprecipes.com" target="_blank">WPRecipes [EN]</a>\',
             \'f.php\' =&gt; \'In die Datei functions.php einfügen.\');
 $text = str_replace_first(array_keys($replace), $replace, $text);
return $text;
}
add_filter(\'the_content\', \'guru20_ReplaceWords\');
add_filter(\'the_excerpt\', \'guru20_ReplaceWords\');

function str_replace_first($from, $to, $subject)
 {
   $from = \'/\'.preg_quote($from, \'/\').\'/\';
    return preg_replace($from, $to, $subject, 1);
 }