Making selected value of option with php - php

Question

I want to make a code which demonstrates that if I choose any option value and press submit button, the value which I chose should be seen in the options box.
The codes are;
<?php
$myfile = fopen("cars_lab5.txt", "r") or die("Unable to open file!");
?>
This is to open the file because I pull the items from a file.
<?php
$index = 0;
$val = $_GET['car'];
//$selection = "";
for ($index=0 ; $index < 5 ; $index++){
$num = 0;
$line = fgets($myfile) . "<br>";
$slide = explode("|",$line);
//echo '<option value="' . $index . '">' . $slide[$num] . ' - ' . $slide[num+1] . ' euros';
if ($val==0){
echo '<option value="' . $index . '"' . $selection . ' selected">' . $slide[$num] . ' - ' . $slide[num+1] . ' euros'; }
else if ($val==1){
echo '<option value="' . $index . '"' . $selection . ' selected">' . $slide[$num] . ' - ' . $slide[num+1] . ' euros'; }
else if ($val==2){
echo '<option value="' . $index . '"' . $selection . ' selected">' . $slide[$num] . ' - ' . $slide[num+1] . ' euros'; }
else if ($val==3){
echo '<option value="' . $index . '"' . $selection . ' selected">' . $slide[$num] . ' - ' . $slide[num+1] . ' euros'; }
else if ($val==4){
echo '<option value="' . $index . '"' . $selection . ' selected">' . $slide[$num] . ' - ' . $slide[num+1] . ' euros'; }
}
fclose($myfile);
?>
When I use this code, everything works properly but if I choose third option and press submit button, again first item is seen on the option box instead of what I choose.

Answer 1

You have set all options with the 'selected' tag, so the browser will show the last option as selected by default.
You need to remove the 'selected' string from the echo statement and configure the $selection var somewhere:
$selection=($index==$val?'selected':null)
You don't need the if/else statement at all.
So you would just have one line:
echo '<option value="' . $index . '"' . $selection . '">' . $slide[$num] . ' - ' . $slide[num+1] . ' euros';
EDIT including example as per comment
Your example code will look like:
<?php
$index = 0;
$val = $_GET['car'];
//$selection = "";
for ($index=0 ; $index < 5 ; $index++){
$num = 0;
$line = fgets($myfile) . "<br>";
$slide = explode("|",$line);
$selection=($index==$val?'selected':null);
echo '<option value="' . $index . '"' . $selection . '">' . $slide[$num] . ' - ' . $slide[num+1] . ' euros';
}
fclose($myfile);
?>