A little doubt online request answer

A small question online request answer
$query = "Select NCC from City";
$result =mysql_query ($query);
while (list ($NCC) = Mysql_fetch_row ($result)) {
$a = $ncc. ', ';
echo $a;
}
$string = "$a";
I want to pass all the NCC values from all databases to $ A so that $string= "all NCC"; How to do it.

------Solution--------------------
$a-";
while (list ($NCC) = Mysql_fetch_row ($result)) {
$a. = $NCC;
}
$string = $a;
------Solution--------------------
$a = ";
$query = "Select NCC from City";
$result =mysql_query ($query);
while (list ($NCC) = Mysql_fetch_row ($result)) {
$a. = $NCC. ', ';
echo $a;
}
$string = "$a";
------Solution--------------------
An equal sign is missing:
$a = ";
while (list ($NCC) = Mysql_fetch_row ($result)) {
$a. = $NCC;
}
$string = $a;
------Solution--------------------
while (list ($NCC []) = Mysql_fetch_row ($result));
Array_pop ($NCC);
$string = Join (', ', $NCC);

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