extract function

thegooner · June 11th, 2004, 03:47 AM

Seeing as everyone was so very helpful with my last query on this forum, I thought I'd ask just one more question about the script in the book I don't totally understand.

The following code is in the book:

$query_d = "SELECT people_fullname
        FROM people
        WHERE people_id='$movie_director'";
    $results_d = mysql_query($query_d) or die(mysql_error());
        $row_d = mysql_fetch_array($results_d);
        extract ($row_d);
        $director = $people_fullname

What exactly does extract do? In the book, this function is used for the first time in this script, with absolutely no explanation of waht it does and when to use it.

Thanks once again

BuzzLY · June 11th, 2004, 06:11 AM

extract is a "quick and dirty" way to take all of the values in an associative array, and put them into variables with the same name as the keys. For example, let's say you have a database of people, and your query returns the first name, last name, and department. Your data row might look like this:

Code:

$employee = array("first_name" => "George",
                  "last_name"  => "Smith",
                  "dept"       => "Accounting");

If you run extract($employee), you will end up with three variables:

Code:

$first_name = "George"
$last_name = "Smith"
$dept = "Accounting"

Make sense?

If you want more information about this, or in fact any function that you need more information on, check the php manual at www.php.net. In fact, accessing the manual is easy. If you know the function you want to look up, just type in www.php.net/functionname and it will take you right to the page. You'll find help for extract() at http://www.php.net/extract.

Hope that helps!

BuzzLY
aka Michael K. Glass
Author, Beginning PHP, Apache, MySQL Web Development

Bunkermaster · June 11th, 2004, 06:15 AM

Hi,

here it is:
if your table 'mytable' has 2 fields: 'field1' and 'field2'
then you query the table as follows:
$sql = "SELECT field1, field2
        FROM mytable
        WHERE field1='foo'";
    $results = mysql_query($sql) or die(mysql_error());
        $row = mysql_fetch_array($results);

$row now holds 2 elements (4 really but it's off topic)
Array{
    [field1]=> 'foo'
    [field2]=> 'bar'
}

Now if you use extract on your $row it will create 2 variables: $field1 with 'foo' as value and $field2 with 'bar' as value.
extract ($row);

Is it more understandable now? You basically create string variables off an array table.

thegooner · June 11th, 2004, 06:44 AM

Thanks once again guys. All is understood.

I wish the php.net site explained things as well as that, as I looked at php.net/extract but it didn't make it too clear.

I quote from the site: "This function is used to import variables from an array into the current symbol table".

Ok, if you know what "the current symbol table" is.

Anyway, thanks a lot.