Något sådant här borde fungera
.
.
.
$q = array();
if(trim($_POST["b"]) !== ""){
$q[] = "Program = :program";
}
if(trim($_POST["c"]) !== ""){
$q[] = "Descr = :descr";
}
if(trim($_POST["d"]) !== ""){
$q[] = "Cost = :cost";
}
if(sizeof($q) > 0){//check if we have any updates otherwise don't execute
$query = "UPDATE links SET " . implode(", ", $q) . " WHERE Id= :id";
$stmt = $dbh->prepare($query);
$stmt->bindParam(":id", $_POST["a"]);
if(trim($_POST["b"]) !== ""){
$stmt->bindParam(":program", $_POST["b"]);
}
if(trim($_POST["c"]) !== ""){
$stmt->bindParam(":descr", $_POST["c"]);
}
if(trim($_POST["d"]) !== ""){
$stmt->bindParam(":cost", $_POST["d"]);
}
$stmt->execute();
}
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.
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