for ($i=0; $i<sizeof(array1); $i++) {
     echo $arrray1[$i];
     echo $arrray2[$i];
}

foreach ($images as $key => $val) {
    echo '<img src="' . $val . '" alt="' . $descriptions[$key] . '" /><br />';
}

$count = count($images);
for ($i = 0; $i < $count; $i++) {
    $image = $images[$i];
    $description = $descriptions[$i];
}

$images = array('image1', 'image2', ...);
$descriptions = array('description1', 'description2', ...);

foreach (array_combine($images, $descriptions) as $image => $desc) {
  echo $image, $desc;
}