My php function will not be called - php

Question

I have the following code to connect between mysql database and android.
$conn = mysqli_connect($servername, $username, $password, $database);
//if there is some error connecting to the database
//with die we will stop the further execution by displaying a message causing the error
if ($conn) {
$response["Connection"] = 1;
}
else {
$response["Connection"] = 0;
}
$userID= $_POST['user_id'];
function recordExists() {
$query = "SELECT * FROM user_table";
$result = mysqli_query($conn, $query);
$response["found"] = "i am here";
while($row=mysqli_fetch_array($result)){
$response["found"] = $row['user_id'];
if($row['user_id']==$userID){
return true;
}
}
return false;
// $result_num_rows = mysqli_num_rows($result);
//
// if($result_num_rows>0) {
// return true; // The record(s) do exist
// }
// return false; // No record found
}
$exists=recordExists();
if ($exists) {
$query = "SELECT * FROM user_table WHERE $userID";
$result = mysqli_query($conn, $query);
$row = mysqli_fetch_array ($result);
$Nickname = array();
if ($row['nickname'] == NULL){
array_push($response["nickname"], "False");
}else{
array_push($response["nickname"], $row["nickname"]);
}
$response["Sync"] = "Already Added";
echo (json_encode($response));
} else {
$UserToBeAdded= $_POST['user_id'];
$NameToBeAdded= $_POST['name'];
$EmailToBeAdded= $_POST['email'];
$UserToBeAdded2 = mysqli_real_escape_string($conn, $UserToBeAdded);
$NameToBeAdded2 = mysqli_real_escape_string($conn, $NameToBeAdded);
$EmailToBeAdded2 = mysqli_real_escape_string($conn, $EmailToBeAdded);
$sql_query = "insert into user_table (user_id, name, email) values ('$UserToBeAdded2', '$NameToBeAdded2', '$EmailToBeAdded2');";
mysqli_query($conn, $sql_query);
$response["ID"] = $UserToBeAdded2;
$response["Name"] = $NameToBeAdded2;
$response["Email"] = $EmailToBeAdded2;
$response["Sync"] = "Just Added";
$response["nickname"] = "False";
echo (json_encode($response));
}
mysqli_close($conn);
from the above code, i can receive responses from the php side. however the following response is not received.
$response["found"] = "i am here";
if u see from my code above, basically the function recordExists() will definitely be called. however the response " i am here" is not encoded in JSON when i emulate the android app. anything wrong?

Answer 1

try to declare the response variable above all functions. so add $response=array();on top of the file.
here you can read up about the scope of php variables:
https://secure.php.net/manual/en/language.variables.scope.php

Answer 2

You have a variable scope issue with the connection variable. Pass the connection variable as a parameter.
recordExists($conn);
Also use prepared statements to prevent sql injection attacks.