How can i post a php foreach loop in my database.

Some comments on your code
1. Your While statement does not have a closing }
2. Look at this code

<option value="'.$t50.'" name="'.$t50.'">50x'.$t50.'</option>

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<options> don't have a name attribute
3. You appear to be looping through your products creating the table but using the same names each time around (see below)
4. You are using $_GET - not a good idea - there is a limit on the length of a URL (GET) - which could become problematic if you have a lot of products you are moving. It also means your submission is not safe if you submit twice - you can end up adding product twice
5. You are not santizing your form variables - trusting that
a) they are present
b) They contain valid data
Is a security watchit

You should consider making your form variables arrays

<select name="size[]">

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Instead of

<select name="size">

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That way when you do

$size = isset($_POST['size']) ? $_POST['size'] : array();

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$size will be an array of sizes
$size[0] will be the size for product 1
$size[1] will be the size for product 2
etc
Example
Look at this example to see what is in the $_POST using arrays as form variables
http://www.marcorpsa.com/ee/t1737.html

There are several issues here, and you might want to consider posting this in E-E Gigs, where you can get a professional to help you.  I can't follow all of it, but I can see some things in the PHP script that cry out for remediation :-)

<?php
include_once '../incluedes/conn_cms.php';//session started here 

// YOU MUST NOT USE A GET-METHOD REQUEST TO UPDATE A DATABASE
 if(isset($_GET['submit_post'])){

            $date = date('Y-m-d');
            $fabric=$_GET['fabric'];
            $size=$_GET['size'];
            
            $desenho=$_GET['desenho'];
            $numero=$_GET['numero'];
            $vari=$_GET['vari'];

            $qnty=$_GET['qnty'];
            $cost=$_GET['cost'];
            $subT=$_GET['subtotal'];


            $pedido=$date." ".$_SESSION['userName']."-".$_SESSION['userLName'];

             // YOU MUST NOT USE EXTERNAL DATA IN A QUERY STRING - IT MUST BE ESCAPED
             $query = "SELECT * FROM almofadas WHERE id_price='$fabric'";
             
             $result = mysqli_query($conn,$query);
             
             // YOU MUST NOT USE $result UNTIL YOU HAVE TESTED FOR SUCCESS
             while($rows = mysqli_fetch_assoc($result)){
                
                // EACH ITERATION THROUGH THE WHILE LOOP OVERWRITES THE VALUE IN $tecido
                $tecido=$rows['tecido'];
            }

            // YOU MUST NOT USE EXTERNAL DATA IN A QUERY STRING - IT MUST BE ESCAPED
            $ins_sql = "INSERT INTO orders (fabric,size,product_quantity,order_id,product_img,product_title,variante,product_cost,product_subtotal) 
                     VALUES ('$tecido', '$size' , '$qnty', '$pedido', '$desenho', '$numero', '$vari', '$cost', '$subT')";
            if ($conn->query($ins_sql) === TRUE) {
                echo "New record created successfully";
                } else {
                
                // YOU MIGHT WANT TO LOG ERROR INFORMATION, SO IT CAN BE USED TO FIX THE ERROR
                echo "Error: " ;
                }
            $conn->close();
             }

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Ray and Julian have already pointed out some fundamental flaws in your code which you'll need to address.

Your friend here is something called a Prepared Statement. It will allow you to create one INSERT query and then loop through your data executing that query. A neat trick to help you loop through your data is to name your form fields using an array syntax - Julian has already alluded to this, but to take it a step further, take a look at this naming convention:

product[1][size]
product[1][desenho]
product[1][numero]
...
product[2][size]
product[2][desenho]
product[2][numero]

You can then loop through your products, one by one, inserting them into the database by executing your query. Here's a very brief overview:

if(isset($_POST['submit_post']))
{
    $stmt = $conn->prepare("INSERT INTO orders (size, desenho, numero) VALUES (?, ?, ?)");
    $stmt->bind_param("sss", $size, $desenho, $numero);

    foreach ($_POST['product'] as $key => $product) {
        extract($product);
        $stmt->execute();
    }
}

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As long as you get the form fields named correctly, and match them to the bind_param call, you can make your life a lot easier :)

look how i did

<?php  
include_once '../incluedes/conn_cms.php'; 
			if(isset($_POST['submit_post']))
		{
			$date = date('Y-m-d');
			$size = isset($_POST['size']) ? $_POST['size'] : array();
			$numero = isset($_POST['numero']) ? $_POST['numero'] : array();
			$vari = isset($_POST['vari']) ? $_POST['vari'] : array();
			$desenho = isset($_POST['desenho']) ? $_POST['desenho'] : array();
			$fabric = isset($_POST['fabric']) ? $_POST['fabric'] : array();
			$size = isset($_POST['size']) ? $_POST['size'] : array();
			$qnty = isset($_POST['qnty']) ? $_POST['qnty'] : array();
			$cost = isset($_POST['cost']) ? $_POST['cost']: array();
			$subtotal = isset($_POST['subtotal']) ? $_POST['subtotal'] : array();
			$total = isset($_POST['total']) ? $_POST['total'] : array();
			$all_products = isset($_POST['all_products']) ? $_POST['all_products'] : array();

			$pedido=$date." ".$_SESSION['userName']."-".$_SESSION['userLName'];

			 $query = "SELECT * FROM almofadas WHERE id_price='$fabric'";
		   	 $result = mysqli_query($conn,$query);
		   	 while($rows = mysqli_fetch_assoc($result)){
		    	$tecido=$rows['tecido'];
		    	$fabric=$tecido;
		   	}

		   	
		    $stmt = $conn->prepare("INSERT INTO orders (fabric,size,product_quantity,order_id,product_img,product_title,variante,product_cost,product_subtotal) 
		    VALUES ('$fabric', '$size' , '$qnty', '$pedido', '$desenho', '$numero', '$vari', '$cost')");
		    $stmt->bind_param($fabric, $size , $qnty, $pedido, $desenho, $numero, $vari, $cost);

		    foreach ($_POST['product'] as $key => $product) {
		    	
		        extract($product);
		        $stmt->execute();
		    }

		}

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i get these errors (the lines match code above)

Notice: Array to string conversion in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 20

Notice: Array to string conversion in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 29

Notice: Array to string conversion in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 29

Notice: Array to string conversion in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 29

Notice: Array to string conversion in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 29

Notice: Array to string conversion in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 29

Notice: Array to string conversion in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 29

Notice: Array to string conversion in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 29

Fatal error: Uncaught Error: Call to a member function bind_param() on boolean in C:\xampp\htdocs\system\clientes\gallery\postOrder.php:30 Stack trace: #0 {main} thrown in C:\xampp\htdocs\system\clientes\gallery\postOrder.php on line 30

You seem to have mixed 2 different ideas into your solutions - part of Julians and part of mine. Have a read through both, and choose 1, and then try and implement that.

As Julian said, create a small, static, sample page and work with that until you understand what's going on.

Please consider stepping back from the "big problems" and getting a foundation in how HTML, CSS, JavaScript, PHP, and MySQL work together.  It's a bit of a journey to get from where you are to where you want to be, but all of us have made that journey and now the work is easier for us, because we had an extended period of structured learning.
https://www.experts-exchange.com/articles/11769/And-by-the-way-I-am-New-to-PHP.html

Based on julian advice,now its working.
The problem is that my hidden inputs values only contains the right value when i refresh the page.

$date = date('Y-m-d');
$size = isset($_POST['size']) ? $_POST['size'] :  array();
$numero = isset($_POST['numero']) ? $_POST['numero'] :  array();
$vari = isset($_POST['vari']) ? $_POST['vari'] :  array();
$desenho = isset($_POST['desenho']) ? $_POST['desenho'] :  array();
$fabrics= isset($_POST['fabric']) ? $_POST['fabric'] :  array();
$size = isset($_POST['size']) ? $_POST['size'] :  array();
$qnty = isset($_POST['qnty']) ? $_POST['qnty'] :  array();
$cost = isset($_POST['cost']) ? $_POST['cost']:  array();
$subtotal = isset($_POST['subtotal']) ? $_POST['subtotal'] :  array();
$total = isset($_POST['total']) ? $_POST['total'] :  array();
$all_products = isset($_POST['all_products']) ? $_POST['all_products'] :  array();
			

$pedido=$date." ".$_SESSION['userName']."-".$_SESSION['userLName'];

		foreach ($fabrics as $fabric)
	 {
               $index = array_search($fabric, $fabrics);

		$query = "SELECT * FROM almofadas WHERE id_price='$fabrics[$index]'";
		$result = mysqli_query($conn,$query);
		while($rows = mysqli_fetch_assoc($result)){
		$tecido=$rows['tecido']; 
	}


$ins_sql = "INSERT INTO orders (fabric,size,product_quantity,order_id,product_img,product_title,variante,product_cost,product_subtotal) 
VALUES ('$tecido', '$size[$index]' , '$qnty[$index]', '$pedido', '$desenho[$index]', '$numero[$index]', '$vari[$index]', '$cost[$index]', '$subtotal[$index]')";
			 	   
	 if ($conn->query($ins_sql) === TRUE) {
	 echo "New record created successfully";
	 } else {
	 echo "Error: " ;
	}
				
}

		   	$conn->close();

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Again basic understanding of how the process works is required.

First question - what function are your hidden inputs serving? With the right AJAX implementation you don't need them.

I am using the php post method and my <td> tags with names[] does not post anything, so i used hidden inputs to hold some data, because inputs works on the post method.
So as you said Julian if i use ajax to post, i won't need the hidden inputs because ajax can get the values from my <td> tags correct?

my <td> tags with names[]

I don't understand

so i used hidden inputs to hold some data,

What data?

because ajax can get the values from my <td> tags correct?

AJAX is a means for communicating with the server - it is a bit of a misnomer as it standards for Asynchronous Javascript and XML - we don't use XML much mostly JSON so should probably be named AJAJ?.
Anyway, in this case AJAX does not do anything per se. You can use JavaScript / jQuery to retrieve any html / value from the document and having done so you can use AJAX to send that information to the server.

But that is beside the point - I am trying to understand why you are storing values in <td> elements at all?

I'm sorry,  i didn't post the code i was referring to.

<td name="qnty[]" class="product'.$id.' " value="'.$value.'">'.$value.'</td>

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 <input  type="hidden" name="qnty[]" value="'.$value.'"/> 

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Here you can see that my name="qnty[]" is in my td tag.(php does not grab this value)


But when i use input the values are sent,but not updated,the only things that updates onclick or onchange in my <td> tags.