Encounter issues when checking prime number in PHP - php

Question

<?php
if (isset($_GET['number'])){ // Loaded for first time?
if(isValid($_GET['number'])){
$isPrime = true;
// Please enter code here
// I have tried the codes here but idk why it cannot seem to work
$i = $_GET(['number']);
if ($number == 1) {
$isPrime = false;
return $isPrime;
}
for ($j = 2; $i <= $number/2; $i++){
if ($number % $i == 0)
$isPrime = false;
return $isPrime;
}
return $isPrime;
// End of code
if ($isPrime) {
echo "<p>".$i." is a prime number!</p>";
} else {
echo "<p>".$i." is not prime.</p>";
}
} else{
// User submitted something which is not a positive whole number
echo "<p>Please enter a positive whole number.</p>";
}
}
// check if the given number is a valid numeric value
// round() rounds a floating point value
function isValid($number) {
if(is_numeric($number) && $number > 0
&& $number == round($number, 0)) {
return true;
}
else {
return false;
}
}
?>
I have tried the above codes, however, I have encountered issues. Please help me out thank you! The codes I have tried are within the // Please enter code here to // End of code
When I run the php file the above image will be shown. The user have to type a number and it will check whether or not the user input is a prime number when user clicks on the "Go!" button.

Answer 1

You had many mistakes.
So I edited the whole code.
here it is:
<?php
if (isset($_GET['number'])) { // Loaded for first time?
if (isValid($_GET['number'])) {
$isPrime = true;
// Please enter code here
// I have tried the codes here but idk why it cannot seem to work
$i = $_GET['number'];
if ($i == 1) {
$isPrime = false;
}
for ($j = 2; $j <= $i / 2; $j++) {
if ($i % $j == 0)
$isPrime = false;
}
// End of code
if ($isPrime) {
echo "<p>" . $i . " is a prime number!</p>";
} else {
echo "<p>" . $i . " is not prime.</p>";
}
} else {
// User submitted something which is not a positive whole number
echo "<p>Please enter a positive whole number.</p>";
}
}
// check if the given number is a valid numeric value
// round() rounds a floating point value
function isValid($number)
{
if (is_numeric($number) && $number > 0
&& $number == round($number)) {
return true;
} else {
return false;
}
}
?>
<form action="index.php" method="get">
<input type="number" name="number">
<input type="submit" value="Go!">
</form>