Co jest źle z pętlą for?

<?php

       $mysql = @ new mysqli ( $db_host, $db_user, $db_password, $local_database );	

        $a1 = " e.obraz ";
	$a2 = " ekran AS e ";
	$a3 = " e.zmienna = '$zmienna' ";

	$a4 = " SELECT $a1 FROM $a2 WHERE $a3 ";

	$a5 = $mysql -> query ( $a4 );

	$a6 = $a5 ->num_rows;

	echo $a6;

	for ( $i = 1; $i == $a6; $i++ )
	{
		$a1 = " e.obraz ";
		$a2 = " ekran AS e ";
		$a3 = " id = '$i' ";

		$a4 = " SELECT $a1 FROM $a2 WHERE $a3 ";
		$a5 = $mysql -> query ( $a4 );
		$a7 = $a5 -> fetch_assoc();

		echo $a7['obraz'];
	}

?>

Co zrobić żeby pobrało niewiadomą ilość danych do osobnych zmiennych w php, co jest źle?