$word[0]="a";  $word[1]="the";  $word[2]="this";

$mark["ann"]=100;  $mark["bob"]=50;  $mark["col"]=9;

$vec[]=1;  $vec[]=3;  $vec[]=5;  $vec[]=7;  $vec[] = 9;
// which is equivalent to
$vec[0]=1;  $vec[1]=3;  $vec[2]=5;  $vec[3]=7; $vec[4] = 9;

$word = array("a", "the", "this");

$marks = array("ann"=>100, "bob"=>50, "col"=>9);

$vec = array(0 => 1, 1 => 3, 2 => 5, 3 => 7, 4 => 9);
// which is equivalent to
$vec = array(1, 3, 5, 7, 9);