How to search text using php if ($text contains "World")

The best solution is my method:

In my method, only full words are detected,But in other ways it is not.

for example:

$text='hello world!'; 

if(strpos($text, 'wor') === FALSE) { 
   echo '"wor" not found in string'; 
}

Result: strpos returned true!!! but in my method return false.

My method:

public function searchInLine($txt,$word){

    $txt=strtolower($txt);
    $word=strtolower($word);
    $word_length=strlen($word);
    $string_length=strlen($txt);
    if(strpos($txt,$word)!==false){
        $indx=strpos($txt,$word);
        $last_word=$indx+$word_length;
        if($indx==0){
            if(strpos($txt,$word." ")!==false){
                return true;
            }
            if(strpos($txt,$word.".")!==false){
                return true;
            }
            if(strpos($txt,$word.",")!==false){
                return true;
            }
            if(strpos($txt,$word."?")!==false){
                return true;
            }
            if(strpos($txt,$word."!")!==false){
                return true;
            }
        }else if($last_word==$string_length){
            if(strpos($txt," ".$word)!==false){
                return true;
            }
            if(strpos($txt,".".$word)!==false){
                return true;
            }
            if(strpos($txt,",".$word)!==false){
                return true;
            }
            if(strpos($txt,"?".$word)!==false){
                return true;
            }
            if(strpos($txt,"!".$word)!==false){
                return true;
            }

        }else{
            if(strpos($txt," ".$word." ")!==false){
                return true;
            }
            if(strpos($txt," ".$word.".")!==false){
                return true;
            }
            if(strpos($txt," ".$word.",")!==false){
                return true;
            }
            if(strpos($txt," ".$word."!")!==false){
                return true;
            }
            if(strpos($txt," ".$word."?")!==false){
                return true;
            }
        }
        }

    return false;
}