PHP: $_POST variables unexistant into functions

Question

I am bringing some info trough $_POST, but when I try to make use of this info into any function, console emerges an error about Undefined Variable (in this example, $ms_img brings an error, as well as $con -the connection query declared on conexionbbdd.php- and any othe variable inside functions.

EDIT: Neither passing as arguments works, it emerges one error per argument as this:

Warning: Missing argument 1 for checkCost(), called in C:\wamp\www...\actions\msg_newMessage.php on line 96 and defined in C:\wamp\www...\actions\msg_newMessage.php on line 17

function checkCost($con,$ms_img,$id){...}

CODE:

<?php
 session_start();
 include("../conexionbbdd.php");
 include("../conexionapi.php");
 $id = $_SESSION['id']; 
 $inclass = $_SESSION['inclass']; 
if($_SESSION['estado'] == 'activo'){
 $ms_content = $_POST['ms_content'];
 $ms_img = $_POST['ms_img'];
 $ms_prefix = $_POST['ms_prefix'];
 $ms_phone = $_POST['ms_phone'];
 function checkCost(){
 $totalCost = 0;
 if ($ms_img!=""){
 $totalCost=2;
 } 
 else{
 $totalCost=1;
 }
 $checkCredits=mysqli_query($con,"SELECT us_credits FROM ws_users WHERE us_id=$id");
 }
 function sendMessage(){
 //WHATEVER
 }
 if($inclass==='1'){ 
 checkCost(); 
 }
 else{
 sendMessage(); 
 }
}else{
header('location:../login.php');
}
?>

• Barmar: You need to pass the variables as arguments to the function or declare them with global.
• fabpico: Do not use glob to inject global vars into a funciton. In long term this can result very confusing code.
• spenibus: possible duplicate of PHP: variable not working inside of function?

Answer 1

You can have access to superglobal variables like $_POST in any function. But global variables such as $con that should be initialized in an including file is not accessable in a function. You can pass it as parameter. And do not use the global keyword to inject global vars into a funciton. In long term this can result very confusing code. So you could do:

function checkCost($con){
 $ms_content = $_POST['ms_content'];
 $ms_img = $_POST['ms_img'];
 $ms_prefix = $_POST['ms_prefix'];
 $ms_phone = $_POST['ms_phone'];
 $totalCost = 0;
 if ($ms_img!=""){
 $totalCost=2;
 } 
 else{
 $totalCost=1;
 }
 $checkCredits=mysqli_query($con,"SELECT us_credits FROM ws_users WHERE us_id=$id");
 }

But its still very procedural. I recommend you to start to read OOP.

• Biomehanika: I do need OOP, that's for sure. But it is still a bit confusing for me. Thank you for your explanation, worked.