how to separate an sql query into chain methods - php

Question

I am new in oop and I am trying to change a sql query into 3 chained method and use like this:
$mtag = $mtag->allTags()->orderBy()->lastThree();
public function allTags()
{
$sql = "SELECT tag_id FROM posts_tags ";
$sql .= "GROUP BY tag_id ";
$sql .= "ORDER BY COUNT(*) DESC LIMIT 3 ";
$res = self::builder($sql);
return $res;
}
i want to use each $sql in to a separate chain method .
how can i do this?
i have tried this but it doesnt work
public function allTags()
{
$sql = "SELECT tag_id FROM posts_tags ";
self::builder($sql);
return $this;
}
public function orderBy()
{
$sql = "GROUP BY tag_id ";
self::builder($sql);
return $this;
}
public function lastThree()
{
$sql = "ORDER BY COUNT(*) DESC LIMIT 3 ";
self::builder($sql);
return $this;
}
my builder method looks like this
public function builder(string $sql)
{
$stmt = $this->database->prepare($sql);
$stmt->execute();
if (!$stmt) {
throw new Exception("Query failed . . .");
}
return $stmt;
}

Answer 1

The problem is that the self::builder($sql); method directly prepares the sql statement, instead of waiting for it to be completely constructed:
$mtag = $mtag
/*
the first self::builder($sql) is called,
prepares the statement without the order and group by
*/
->allTags()
/*
the second self::builder($sql) is called from orderBy, prepares "GROUP BY tag_id "
probably a syntax error is hidden here
*/
->orderBy()
/*
the third self::builder($sql) is called from lastThree
it tries to prepare "ORDER BY COUNT(*) DESC LIMIT 3 "
a syntax error is probably hidden here too
*/
->lastThree();
The statement is prepared over and over again. You can avoid this by doing, in that order
defining the statement with all its chained variants
calling a method to fetch data, preparing the statement composed from the various chained method calls.
$stmt = $mtag->allTags()->orderBy()->lastThree();
$result = $stmt->resolve();
where $stmt = $this->database->prepare($sql); only happens in the resolve method.

Answer 2

you have error in return code.
Change to that code!
public function lastThree()
{
$sql = "ORDER BY COUNT(*) DESC LIMIT 3 ";
$res = self::builder($sql);
return $res;
}