PHP scope issue within while loop - php

Question

Trying to teach myself php and I am struggling with what I think is a scoping issue?
I have a query, while loop, if/else and a function.
I would like to echo the results of the function get_patronapi_data($id) within my while loop.
My code so far is as follows (stripped for legibility);
$stmt = $conn->prepare("SELECT... ..."); //QUERY here ...
if( $stmt->num_rows > 0 )
{
while ($stmt->fetch()) {
if (SomethingIsTrue){
echo get_patronapi_data($id);
}
else {
echo $somethingElse;
}
}//end while
}//end if
define("APISERVER", "http://mydomain:4500");
function get_patronapi_data($id) {
$apiurl = "APISERVER" . "/PATRONAPI/$id/dump";//line 135
$api_contents = get_api_contents($apiurl);
$api_array_lines = explode("\n", $api_contents);
foreach($api_array_lines as $line){
if(strpos($line, "EXP DATE") !== false){
$data = explode("=", $line);
return $data[1];
}//end if
}//end foreach
}//end function
function get_api_contents($apiurl) {
$api_contents = file_get_contents($apiurl);//line 154
$api_contents = trim(strip_tags($api_contents));
return $api_contents;
}//end function
echo get_patronapi_data($id); // this works and echoes $data on screen
Whenever I echo get_patronapi_data($id); outside of the functions I successfully see the data on screen. However when I echo get_patronapi_data($id); within the loop I receive the following errors;
Notice: Use of undefined constant APISERVER - assumed 'APISERVER' in
C:\xampp...search_1.php on line 135
Warning: file_get_contents(APISERVER/PATRONAPI/3047468/dump): failed
to open stream: No such file or directory in C:\xampp...search_1.php
on line 154
I'm sure I am doing something very silly however any help is appreciated.

Answer 1

Putting some of my comments to an answer.
You need to remove the quotes from:
$apiurl = "APISERVER" . "/PATRONAPI/$id/dump";
^ ^ <<< remove those
since that's treated as a string literal, rather than a constant.
It is declared in:
define("APISERVER", "http://mydomain:4500");
Reference:
http://php.net/manual/en/function.constant.php
Then your connection is out of scope and should be used inside your function(s).
I.e.:
function get_patronapi_data($conn, $id)
and do that for all your functions requiring a connection for them.
You will need to make sure that all folders/files have proper permissions to be written to.

Answer 2

The missing link is the statement:
$data = get_patronapi_data($id);
you should put before echo $data;.
It calls the function get_patronapi_data() passing the value of variable $id as argument and stores the values the function returns in the variable $data.
The variable $data you echo() is not the same as the one used by the function. They use the same name but they are different (I hope you don't use the keyword global in the function).
Read more about functions in the PHP documentation.
The updated (fragment of) code looks like:
if (SomethingIsTrue) {
$data = get_patronapi_data($id);
echo $data;
} else {
echo $somethingElse;
}
If you don't do further processing on the value returned by the function, you can, as well, remove the temporary variable $data from the code fragment above and just use:
if (SomethingIsTrue) {
echo get_patronapi_data($id);
} else {
echo $somethingElse;
}

Answer 3

Assuming you want to print the data from the get_patronapi_data() every iteration in the while loop, you need to actually call the method instead of using $data. Right now you're trying to print something called $data, though you never set a value to it. The $data you return in the function cannot be used outside of that function, so it does not exist in the while loop.
What you could do in your while loop is $data = get_patronapi_data();, and then echo $data. However, you can just echo get_patronapi_data(); first.
If you only want to call your function once, you need to set a variable before you start your while loop (i.e. $variable = get_patronapi_data()), and then use that variable in your while loop (i.e. echo $variable);

Answer 4

I'm not sure I fully understand your question. What happens if you just put
echo get_patronapi_data($id);
in the loop instead of
echo $data;
? As written, you're not calling the function in the loop.