Replace first occurence of a word with link [closed]

by

Try this : 

 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)
 {
   $from = "https://wordpress.stackexchange.com/".preg_quote($from, "https://wordpress.stackexchange.com/")."https://wordpress.stackexchange.com/";
    return preg_replace($from, $to, $subject, 1);
 }

You can try with preg_replace