Insert query doesn't work on server - php

Question

Below code runs without any problems on my local server. However, when I try to run it on the intended server, two of my queries don't work - they do not INSERT as they are supposed to. I've marked two queries that don't work with comments, the rest works. Intended server runs on PHP 5.6.30-0+deb8u1.
UPDATE: thanks to aynber, I've tracked the error. This is the error for the first query: prepared statement \"editRecord\" does not exist" I don't understand why this works on local server but not on intended one.
UPDATE 2: error between prepared statement and execution: syntax error at or near \"ON\"\nLINE 3:
case "editRecord":
$id = openPandoraBox(post("id"));
$tutorAbsence = post("tutorAbsence");
$clientAbsence = post("clientAbsence");
if($tutorAbsence == "1") {
if(post("tutor") != "0") {
// ------------this query does not work.-----------
$absUpsSql = "INSERT INTO tutorabsence(id, tutorid, reason)
VALUES ($1, $2, $3)
ON CONFLICT (id)
DO UPDATE SET tutorid=$2, reason=$3";
$absUpsPrep = pg_prepare($conn, 'editRecord', $absUpsSql);
$absUpsQry = pg_execute($conn, 'editRecord',
array($id, post("tutor"), post("tutorreason"))
);
} else {
$tutorAbsence = "0";
};
} else {
$absDelSql = "DELETE FROM tutorabsence WHERE id=$1";
$absDelPrep = pg_prepare($conn, 'absDel', $absDelSql);
$absDelQry = pg_execute($conn, 'absDel', array($id));
};
if($clientAbsence == "1"){
if(post("client") != "0") {
// ------------this query does not work.-----------
$absUpsSql = "INSERT INTO clientabsence(id, clientid, reason)
VALUES ($1, $2, $3)
ON CONFLICT (id)
DO UPDATE SET clientid=$2, reason=$3";
$absUpsPrep = pg_prepare($conn, 'absUps', $absUpsSql);
$absUpsQry = pg_execute($conn, 'absUps',
array($id, post("client"), post("clientreason"))
);
} else {
$clientAbsence = "0";
};
} else {
$absDelSql = "DELETE FROM clientabsence WHERE id=$1";
$absDelPrep = pg_prepare($conn, 'absDelOne', $absDelSql);
$absDelQry = pg_execute($conn, 'absDelOne', array($id));
};
$resultSql = "UPDATE appointments
SET hour=$1, tutorid=$2,
clientid=$3, purpose=$4,
tutornotshown=$5, clientnotshown=$6
WHERE appid=$7";
$resultPrep = pg_prepare($conn, 'resultSql', $resultSql);
$result = pg_execute($conn, 'resultSql',
array(post('hour'), post("tutor"), post("client"),
post("purpose"), $tutorAbsence, $clientAbsence, $id
)
);
echo json_encode(array("success" => 1));
break;

Answer 1

UPDATE 2: error between prepared statement and execution: syntax error at or near \"ON\"\nLINE 3:
If it works on your local server but not on production server, it is likely that they don't run the same version of PostgreSQL. ON CONFLICT is a feature that was released with PostgreSQL 9.5 (https://www.postgresql.org/docs/9.5/static/sql-insert.html) which is still fairly recent.
You should run this query on the production server to check out which version of PostgreSQL it uses:
SELECT version();
Your server probably runs PostgreSQL 9.5 or 9.6 while the production server is probably on an older release.

Answer 2

Upsert for PostgreSQL below 9.5 is too complicated. I am very short of time, so I'll just use SELECT COUNT(*) and if's.