how to show selected dropdown value after submit on same page - php

Question

There is two drop-down list having different values and a submit button. after submiting it the action is on the same page with $_SERVER['PHP_SELF']; now i want to show the selected dropdown value after the report is generated but i cant figure out how to do that.
<form name="gg" method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<table align="center">
<tr>
<th>
<label>Center Name:</label>
</th>
<td>
<select name="center_name" id="centername" required >
<option value="">Select Center</option>
<option value="xxx">XXX</option>
</select>
</td>
</tr>
<tr>
<th>
Age:
</th>
<td>
<select name="age_bracket" id="agebracket" required >
<option value="" >Select Age</option>
<option value="18-24" >18-23</option>
<option value="25-34" >25-34</option>
<option value="35-44" >35-44</option>
<option value="45-54" >45-54</option>
<option value="55-64" >55-64</option>
<option value="65-74" >65-74</option>
<option value="75" >75+</option>
</select>
</td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" name="submit" value="Submit"></td>
</tr>
<?php
//db connection goes here
echo "<table style='width:70%' table border='1' style='table-layout:fixed' align='center'>";
echo "<tr>
<th>No</th>
<th>col1</th>
<th>col2</th>
<th>col3</th>
<th>col4</th>
</tr>";
if(isset($_POST['submit'])) {
//processing request here
//echo fetched rows
result comes like this
centername:-
age:-
submit
slno col1 col2 col3 col4
//after submit i get the report fetched here on the same page but could not get the selected drop-down values

Answer 1

I don't understand your question very well... I have read your comments... I think you want something like this?
<form name="gg" method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<table align="center">
<tr>
<th>
<label>Center Name:</label>
</th>
<td>
<select name="center_name" id="centername" required >
<option value="">Select Center</option>
<option value="xxx"<?php if(isset($_POST["center_name"]) && $_POST["center_name"] == "xxx") { echo " selected"; } ?>>XXX</option>
</select>
</td>
</tr>
<tr>
<th>
Age:
</th>
<td>
<select name="age_bracket" id="agebracket" required >
<option value="" >Select Age</option>
<option value="18-24"<?php if(isset($_POST["age_bracket"]) && $_POST["age_bracket"] == "18-24") { echo " selected"; } ?>>18-23</option>
<option value="25-34"<?php if(isset($_POST["age_bracket"]) && $_POST["age_bracket"] == "25-34") { echo " selected"; } ?>>25-34</option>
<option value="35-44"<?php if(isset($_POST["age_bracket"]) && $_POST["age_bracket"] == "35-44") { echo " selected"; } ?>>35-44</option>
<option value="45-54"<?php if(isset($_POST["age_bracket"]) && $_POST["age_bracket"] == "45-54") { echo " selected"; } ?>>45-54</option>
<option value="55-64"<?php if(isset($_POST["age_bracket"]) && $_POST["age_bracket"] == "55-64") { echo " selected"; } ?>>55-64</option>
<option value="65-74"<?php if(isset($_POST["age_bracket"]) && $_POST["age_bracket"] == "65-74") { echo " selected"; } ?>>65-74</option>
<option value="75"<?php if(isset($_POST["age_bracket"]) && $_POST["age_bracket"] == "75") { echo " selected"; } ?>>75+</option>
</select>
</td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" name="submit" value="Submit"></td>
</tr>
</table>
</form>
To get the select values you can simply:
<?php
echo $_POST['center_name'];
echo $_POST['age_bracket'];
?>
You can remove <?php echo $_SERVER['PHP_SELF']; ?> from action as well.

Answer 2

<?php
echo "centername:".$_POST['center_name'];
echo "Age:" $_POST['age_bracket'];
?>
<form name="gg" method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<table align="center">
<tr>
<th>
<label>Center Name:</label>
</th>
<td>
<select name="center_name" id="centername" required >
<option value="">Select Center</option>
<option value="xxx">XXX</option>
</select>
</td>
</tr>
<tr>
<th>
Age:
</th>
<td>
<select name="age_bracket" id="agebracket" required >
<option value="" >Select Age</option>
<option value="18-24" >18-23</option>
<option value="25-34" >25-34</option>
<option value="35-44" >35-44</option>
<option value="45-54" >45-54</option>
<option value="55-64" >55-64</option>
<option value="65-74" >65-74</option>
<option value="75" >75+</option>
</select>
</td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" name="submit" value="Submit"></td>
</tr>
</form>