Programmer - matching the individual words from array

// I am working on matching the individual words from array $frequency
// to the search results from that individual word.

I don't know why this does not work

for ($i = 1; $i <= ($frequency); $i++) {

    echo $i;


    echo getphp_AlexVortaro ($frequency[$i]);
    echo getphp_Smartfm($frequency[$i]);
    print_r($frequency[$i]);


}

I get

Notice: Undefined offset: 11 in /Users/briancarpenter/Sites/Vortoj/countplus.php

on line 21

X A lot