如何在不使用提交按钮的情况下获得下拉选择的值？

Question

I want to store the dropdown selected value, and I want to pass that selected value to next page.To do this I want to store the drop down selected value with our using any button. By using submit button I can do this.

My code is,

<?php
include_once 'Connection.php';
$sql = "select project_name from project";
$result_sql = mysqli_query($db,$sql);
echo '<form action="#" method="post">
<select name="project_name" id="project_name">';
        while ($row = mysqli_fetch_array($result_sql)) {
                echo "<option>" . $row['project_name'] ."</option>";    
            }
echo'</select>
<input type="submit" name="submit" value="Get Selected Values" />
</form>';

if(isset($_POST['submit'])){
$selected_val = $_POST['project_name'];  // Storing Selected Value In Variable
//echo "You have selected :" .$selected_val;  // Displaying Selected Value
}
?>

Answer 1

Since PHP is run on the server (and not on the client like JavaScript), the form has to be submitted one way or another so that your PHP code is run. You can submit a form either with a submit button, with JavaScript or by pressing enter from a text input field.

Depending on how you submit the form, $_POST['submit'] may not always be set. You should check if $_POST['project_name'] is set instead.