A simple loop

Anon

This is kind of a weird question:

i have a table with three rows: id, name, position, and email. the table name is staff.

I wanted to write a script to list all the members in the table, and i did - it works. Here's the thing, though: it was a fluke, i have no idea how my script works! for all i know it could be an infinite loop that simply works then times out after 30 seconds. Can someone go through this and explain it to me step by step?

<?
$query = "SELECT * FROM staff ORDER BY id";
$result = mysql_query($query);

while ($r = mysql_fetch_array($result)) {

echo "$r[0]";
echo "$r[1]";
echo "$r[2]";
echo "$r[3]";
}
?>

Forget about printing formated output - i can do that later, right now all it does is mash the results together in a long line, but don't worry about it. i just want to know what it's doing.

I told you this was a weird question 😛

thank you.

Anon

$query = "SELECT * FROM staff ORDER by id";

That sets some text into a variable $query.

$result = mysql_query($query);

That stores the result of the sql query ($query) into the variable $result. Understand that you basically just passed SELECT * FROM staff ORDER by id into mysql_query which returned a multidimensional array called $result. Which in turn you use mysql_fetch_array to pull a row entry from and return an array (or maybe a hash array if i remember correctly).

while($r = mysql_fetch_array($result)) {

indicates take the next row (or the first row if its at the beginning) from the result of the mysql query (which you obtained by running mysql_query), put it (the array of the columns in the row it pulled) into $r, and if $r is defined, keep looping. When $r becomes undefined (or in other words mysql_fetch_array returns that it's at the end of all the data in the table) it exits out. The statement above is commonly used to loop through all the data returned from a mysql query.

the echo statements just print the data out...

Very simply this loop through the data and prints the information to the screen.

sepodati

Okay...There are rows and columns in your database. The elements like id,name,position, and email are columns. The individual entries for each person are rows. Think of it as a spreadsheet of sorts...

$query = "...";

This defines your query that you're sending to the database. Your query is saying select every column (SELECT *) from the staff table and put them in order by the id number. The order defaults to ascending (ASC). You can use DESC for decending. Since there is no WHERE clause on your query, every row is selected.

$result = mysql_query($query);

This actually sends the query to the database. $result is not the data returned from the query. It's a pointer of sorts that you use to get the data or number or rows returned.

while($r = mysql_fetch_array($result))

This creates your loop. mysql_fetch_array($result) goes and gets the first row from the result set returned by your query. Each time you call mysql_fetch_array($result), it'll go to the next row. The row is assigned to the array $r. The first column in your database is assigned to $row[0], the second to $row[1], etc... You can also use the name of the column as the key in your array. Assuming you have an id,name,position, and email column in your table, and they are in that order...

$row[0] -> $row[id] -> id column
$row[1] -> $row[name] -> name column
$row[2] -> $row[position] -> position column
$row[3] -> $row[email] -> email column

Once the last row is fetched, mysql_fetch_array() will return false, so that will end your while loop.

Hope that helped. Now go read the rest of the manual.

---John Holmes...

sepodati

I guess I type to slow... 🙂

---John Holmes...

Anon

thank you everyone! 🙂

what a loser i am typing working code then wondering what it does! 🙂