Someone

$input_string = "This is a test";

$exclude_words=array("about","above","after","again","all","also","am","an","and","any","are","as","at","back","be","been","before","behind","being","below","but","by","can","click","do","does","done","each","else","etc","ever","every","few","for","from","generally","get","go","gone","has","have","hello","here","how","if","in","into","is","it","just","keep","later","let","like","lot","lots","made","make","makes","many","may","me","more","most","much","must","my","need","no","not","now","of","often","on","only","or","other","others","our","out","over","please","put","so","some","such","than","that","the","their","them","then","there","these","they","this","try","to","up","us","very","want","was","we","well","what","when","where","which","why","will","with","within","you","your","yourself");

$new_string = str_replace($exclude_words, "", $input_string);

$words = explode(" ", $new_string);

foreach( $words as $word ) {

  if( strlen($word) > 2 ) {
     $newArray[] = $word;
  }
}

$search_string = implode(" ", $newArray);