Upload Images as array

I am trying to upload multiple images to a folder and is working properly. I have a problem when i am trying to store the name of images in database. If i upload just one is working. If i upload more than one I get just one name in my database.

Whats the way to upload, making an array with images titles, to my db?

Here is the code:

<div id="maindiv">
<div id="formdiv">
    <h4>Upload Image for </h4>
    <form enctype="multipart/form-data" action="" method="post">
        <p class="alert alert-info">Only JPEG,PNG,JPG Type Image Uploaded. Image Size Should Be Less Than 100KB.</p>
        <hr/>
        <div id="filediv"><input name="file[]" type="file" id="file"/></div><br/>
        <input type="button" id="add_more" class="upload" value="Add More Files"/>
        <input type="submit" value="Upload File" name="add_images" id="upload" class="upload"/>
    </form>
</div>

And here is my php:

if (isset($_POST['add_images'])) {
$j = 0; 
$target_path = "images/";
for ($i = 0; $i < count($_FILES['file']['name']); $i++) {
    $validextensions = array("jpeg", "jpg", "png");  
    $ext = explode('.', basename($_FILES['file']['name'][$i]));//store extensions in the variable
    $name_of_img = basename($_FILES['file']['name'][$i]);
    $target_path = $target_path . $name_of_img;
    $j = $j + 1;
      if (($_FILES["file"]["size"][$i] < 1000000) 
            && in_array($file_extension, $validextensions)) {
        if (move_uploaded_file($_FILES['file']['tmp_name'][$i], $target_path)) {
            echo $j. ').<span id="noerror">Image uploaded successfully!.</span><br/><br/>';
            print_r($name_of_img);
            $query = "UPDATE post SET ";   
            $query .= "images = '{$name_of_imgs}' ";
            $query .= "WHERE post_id = {$the_post_id}";    
            $update_cruise_img = sqlsrv_query($con, $query);  
        } else {
            echo $j. ').<span id="error">please try again!.</span><br/><br/>';
        }
    } else {//if file size and file type was incorrect.
        echo $j. ').<span id="error">Wrong file Size or Type</span><br/><br/>';
    }
}
 }

I tried by creating array like this $name_of_imgs = json_encode($_POST['file']); but is not working