trouble comparing two arrays

Matt_Parsons

I am creating two arrays.
Each array is formed from a select statement in mysql.

I want to create a new array from the two arrays with all the values that are not in both, i.e, if the value Matt is in both arrays then leave it out.

I have this so far

$result=mysql_query ("select * from performances WHERE gameplayed='33'");
$names = MYSQL_NUM_ROWS($result);
while ($myrow = mysql_fetch_array ($result))
{
$outputplayers[] = $myrow[playername];
}

$result=mysql_query ("select * from teams WHERE category='Under10'");
$names1 = MYSQL_NUM_ROWS($result);
while ($myrow = mysql_fetch_array ($result))
{
$outputplayers2[] = $myrow[playername];
}

then i compare the two using:
$arraydiff2 = array_diff ($outputplayers,$outputplayers2);

Any help would be appreciated

ednark

my recent reading of the array functions gives me this solution

[man]array_diff[/man]( $arr1, $arr2 )

see if that is what you are looking for

Matt_Parsons

I have tried using

array_diff( $arr1, $arr2 ) but using my own arrays i.e.

$arraydiff2 = array_diff ($outputplayers,$outputplayers2);

but when i output the result of $arraydiff2 its empty!

Weedpacket

"Values that are not in both"
"Values that are in either one but not in the other" (assuming we don't want to include elements that are in neither array...)
"Values that, if one is in the first it's not in the second; and if it's in the second, not in the first"

Oh, of course.

"Values that are in one or the other, but not in both."
(A U 😎 - (A n 😎

Appropriate algebra or a handy Venn diagram may well provide different formulations.

Don't be shy, of course it will:

(A - 😎 n (B - A)
Gee, that's just "Values that, if one is in the first it's not in the second; and if it's in the second, not in the first" again.

All's fair in love and programming

ednark

sql is best for doing set logic... the first thing you should think of when you see the U and n is sql...

so why not push your diff into sql

SELECT
    *
FROM
    teams, performances
WHERE
    teams.category = 'Under10'
    AND
    performances.gameplayed = '33'
    AND
    teams.playername <> performances.playername

as Weedpacket suggested

(A U 😎 - (A n 😎

(A U 😎 is handled by ( FROM teams, performances )

(A n 😎 is handled by the ( teams.playername <> performances.playername )

i think thats right...

give it a try

[edit]

after looking at this again i think its wrong... ill figure out something better for you later... hmmm... i never tested it before i put it up

Weedpacket

...funny, I could've sworn PHP had array_union() .... array_unique(array_merge()) seems so excessive, don't you agree?

I agree with ednark that it would be better to do this in SQL if the data is coming from a SQL database. If you can do the logic there - do so; the database is much better at this sort of thing than the more general-purpose PHP engine, minimises the amount of data that has to be transferred from the database to PHP over the connection, and minimises the size of the result set that has to be stored in PHP and read through.

I guess the WHERE clause would look something like

WHERE (this AND NOT that) OR (that AND NOT this)

where this and that are the required conditions. An equivalent would be

WHERE (NOT this OR NOT that) AND (that OR this)

Matt_Parsons

I have got it working.
I could not use sql to do the logic for me as the select statements were querying two different tables.
I used the line

$arraydiff2 = array_diff ($outputplayers,$outputplayers2); on both my arrays and it works. I had two problems which caused me to do this post. The first problem was not outputting the contents of the array properly. The second problem was that my test data had changed someone else was working with it, and the arrays ended up identicle therefore the was nothing in the array diff.

thanks for all the help i truly appreciate it.

Matt