Php Notice: Use of undefined constant - constants

Question

What am i doing wrong ?
echo try_add("test","2562782");
echo try_add("test","25627826");
function try_add($ct,$tankid){
$file = 'testFile_'.$ct.'.txt';
$pizza = file_get_contents($file);
preg_match_all("/Tankid:(?P.*?);/", $pizza, $pie);
//print_r($pie);
//outputs
//Array
//(
// [0] => Array
// (
// [0] => Tankid:2562782;
// [1] => Tankid:25627826;
// [2] => Tankid:2562782;
// [3] => Tankid:25627826;
// )
//
// [this] => Array
// (
// [0] => 2562782
// [1] => 25627826
// [2] => 2562782
// [3] => 25627826
// )
//
// [1] => Array
// (
// [0] => 2562782
// [1] => 25627826
// [2] => 2562782
// [3] => 25627826
// )
//
//)
foreach($pie[this] as $thi){
if($thi == $tankid){
$inthis = "yes";
}
else{
$inthis = "no";
}
}
if($inthis == "no"){
$myFile = "testFile_$ct.txt";
$fh = fopen($myFile, 'a');
$stringData = "Tankid:$tankid;\n";
fwrite($fh, $stringData);
fclose($fh);
return "This '$tankid' has been added in this file '$myFile' \n";
}
else{
return "This '$tankid' is already in this file '$myFile' \n";
}
}
//Code outputs
//Notice: Use of undefined constant this - assumed 'this' in \xampp\htdocs\new.php on line 39
//This '2562782' has been added in this file 'testFile_test.txt'
//Notice: Use of undefined constant this - assumed 'this' in \xampp\htdocs\new.php on line 39
//This '25627826' has been added in this file 'testFile_test.txt'

Answer 1

Change
foreach($pie[this] as $thi){
Into
foreach($pie['this'] as $thi){

Answer 2

You just need to rewrite
foreach($pie[this] as $thi){
into
foreach($pie[$this] as $thi){
You could even use
foreach($pie as $thi){