How to get 'select' value and put into 'input' value? - php

Question

I have a for with a select dropdown option. I want to get the value that is selected and put it into a hidden input value. I'm trying this at the minute -
echo '<form method="post" action="cart_update.php">';
echo"<select name='qty'>
<option value=1>1</option>
<option value=2>2</option>
<option value=3>3</option>
<option value=4>4</option>
<option value=5>5</option>
<option value=6>6</option>
<option value=7>7</option>
<option value=8>8</option>
<option value=9>9</option>
<option value=10>10</option>
</select>";
echo '<input type="hidden" name="product_qty" value="'.$_GET['qty'].'" />';
echo"</form>;
When I submit this to cart-update.php it tells me that qty is an undefined index on the hidden input line.
Can anyone see the problem?

Answer 1

You will have to use javascript or jQuery. Some sample jQuery code:
$('select').change(function() {
var val1 = $('select').val();
$('your selector').val(val1);
});

Answer 2

Consider this instead:
$arr = array(1,2,3,4,5,6,7,8,9,10);
foreach($arr as $n){
$selected = $n == $_POST['qty'] ? 'selected' : '';
echo "<option value='$n' $selected>$n</option>";
}

Answer 3

Based on #Undefined_variable answer:
/***************************/
jQuery( document ).ready(function( $ ) {
/* selecy key from list , insert into field */
$('#select_start_key').change(function(){
var val1 = $('#select_start_key').val();
$('#start_key').val(val1);
/*reset the select to none*/
$('#select_start_key').val("");
});
});
View example :
https://jsfiddle.net/alinrzv/aj619Lbb/

Answer 4

A few problems:
1. Your form is in POST method, and you are trying to get the value in "Get" method ($_GET)
2. The value of $_GET will be available only after submitting the form.
You should use javascript to get the value. something like that:
<form method="post" action="cart_update.php">
<select name='qty' onChange='document.getElementById("product_qty").value = this.value'>
<option value=1>1</option>
<option value=2>2</option>
<option value=3>3</option>
<option value=4>4</option>
<option value=5>5</option>
<option value=6>6</option>
<option value=7>7</option>
<option value=8>8</option>
<option value=9>9</option>
<option value=10>10</option>
</select>
<input type="hidden" id="product_qty" name="product_qty" value="1" />