Php advance form - php

Question

I am working on CMS project and dealing with form which is adding information into mysql. Everything is working fine but the "textarea" seems like too simple even with tinymce. I am looking for any advice that help to improve the "texarea" such as add multiple images ( mine is only allowed one).
Thanks you and please abandon my bad English
Here is my code:
<script src="https://cloud.tinymce.com/stable/tinymce.min.js"></script>
<script>tinymce.init({ selector:'textarea' });</script>
<form method="post" action="insert_post.php" enctype="multipart/form-data">
<table width="800" align="center" border="10">
<tr>
<td align="center" bgcolor="yellow" colspan="6"><h1>Insert New Post Here</h1></td>
</tr>
<tr>
<td align="right">Post Title:</td>
<td><input type="text" name="post_title" size="30"></td>
</tr>
<tr>
<td align="right" bgcolor="#FF6600"><strong>Post Category:</strong></td>
<td>
<select name="cat">
<option>Select a Category</option>
<?php
include("includes/connect.php");
$get_cats = "select * from catelogries";
$run_cats = mysql_query($get_cats);
while ($cats_row=mysql_fetch_array($run_cats)){
$cat_id=$cats_row['cat_id'];
$cat_title=$cats_row['cat_title'];
echo "<option value='$cat_id'>$cat_title</option>";
}
?>
</select>
</td>
</tr>
<tr>
<td align="right">Post Author:</td>
<td><input type="text" name="post_author" size="30"></td>
</tr>
<tr>
<td align="right">Post Keywords:</td>
<td><input type="text" name="post_keywords" size="30"></td>
</tr>
<tr>
<td align="right">Post Image:</td>
<td><input type="file" name="post_image"></td>
</tr>
<tr>
<td align="right">Post Content:</td>
<td><textarea name="post_content" cols="30" rows="15"></textarea></td>
</tr>
<tr>
<td align="center" colspan="6"><input type="submit" name="submit" value="Publish Now"></td>
</tr>
</table>
<?php
if(isset($_POST['submit'])){
$post_title = $_POST['post_title'];
$post_date = date('m-d-y');
$post_cat = $_POST['cat'];
$post_author = $_POST['post_author'];
$post_keywords = $_POST['post_keywords'];
$post_content = $_POST['post_content'];
$post_image= $_FILES['post_image']['name'];
$post_image_tmp= $_FILES['post_image']['tmp_name'];
if( $post_title=='' or $post_cat=='null' or
$post_author=='' or $post_keywords=='' or
$post_content=='' or $post_image=='')
{
echo "<script>alert('Any of the fields is empty')</script>";
exit();
} else {
move_uploaded_file($post_image_tmp,"../images/$post_image");
$insert_posts = "insert into posts
(category_id,post_title,post_date,
post_author,post_image,post_keywords,
post_content)
values ('$post_cat','$post_title','$post_date',
'$post_author','$post_image','$post_keywords',
'$post_content')";
mysql_query($insert_posts);
echo "<script>alert('post published successfuly')</script>";
exit();
}
}
?>