$req = array(
        'wd[wd1][amount]' => 1.00,
        'wd[wd1][address]' => 'address',
        'wd[wd1][currency]' => 'USD',
        'wd[wd2][amount]' => 0.0001,
        'wd[wd2][address]' => 'address',
        'wd[wd2][currency]' => 'USD',
        'wd[wd3][amount]' => 0.0001,
        'wd[wd3][address]' => 'address',
        'wd[wd3][currency]' => 'USD',
        'wd[wd4][amount]' => 0.01,
        'wd[wd4][address]' => 'address',
        'wd[wd4][currency]' => 'USD',
);

for($i=0;$i<count($address_ary);$i++){
$n=$i+1;

$str.= "'wd[wd".$n."][amount]' => 1.00,
        'wd[wd".$n."][address]' => '".$address_ary[$i]."',
        'wd[wd".$n."][currency]' => 'USD',";
}

$req = array(
       $str,
);