PHP - Fatal error when calling function (undefined function error)

Question

I have a newbie issue with PHP functions calls. File:

    <?php
        session_start();
        include("../conexionbbdd.php");
        include("../conexionapi.php");

        $id = $_SESSION['id'];   
        $inclass = $_SESSION['inclass'];   

    if($_SESSION['estado'] == 'activo'){

        if($inclass==='1'){       
            checkCost();        
        }
        else{
            sendMessage();        
        }

function checkCost(){
    //DO WHATEVER
}

function sendMessage(){
    //DO WHATEVER
}


}else{

header('location:../login.php');

}
?>

Console emerges an error ( ! ) Fatal error: Call to undefined function checkCost() in C:\wamp\www[removedbyme]\actions\msg_newMessage.php on line 14

Answer 1

Functions must be declared before they are used.

This will work:

function doSomething(){

}

doSomething();

This won't:

doSomething();

function doSomething(){

}

Answer 2

Try this:

       session_start();
        include("../conexionbbdd.php");
        include("../conexionapi.php");

function checkCost(){
    //DO WHATEVER
}

function sendMessage(){
    //DO WHATEVER
}


        $id = $_SESSION['id'];   
        $inclass = $_SESSION['inclass'];   

    if($_SESSION['estado'] == 'activo'){

        if($inclass==='1'){       
            checkCost();        
        }
        else{
            sendMessage();        
        }



}else{

header('location:../login.php');

}

Answer 3

PHP code is read from top to bottom, so when you call checkCost, php is not aware that checkCost exist:

<?php
    session_start();
    include("../conexionbbdd.php");
    include("../conexionapi.php");
    function checkCost(){
    //DO WHATEVER
    }

    function sendMessage(){
    //DO WHATEVER
    }
    $id = $_SESSION['id'];   
    $inclass = $_SESSION['inclass'];   

    if($_SESSION['estado'] == 'activo'){

       if($inclass==='1'){       
           checkCost();        
       }
       else{
           sendMessage();        
       }

    }else{

    header('location:../login.php');

   }
?>