Array differences
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From: "Ashley M. Kirchner" on 14 Apr 2010 10:29 On 4/14/2010 2:39 AM, Ashley Sheridan wrote: > On Tue, 2010-04-13 at 23:01 -0600, Ashley M. Kirchner wrote: >> $array1 = array("12", "34", "56", "78", "90"); >> $array2 = array("12", "23", "56", "78", "89"); >> >> $diff1 = array_diff($array1, $array2); >> $diff2 = array_diff($array2, $array1); >> >> $result = array_unique(array_merge($diff1, $diff2)); >> >> print_r($result); >> > > I don't see any problems with doing it that way. This will only work > as you intended if both arrays have the same number of elements I > believe, otherwise you might end up with a situation where your final > array has duplicates of the same number: > > $array1 = $array(1, 2, 3, 4, 5, 6); > $array2 = $aray(1, 3, 2, 5); Wouldn't array_unique() take care of that though? Your example above returns 4 and 6, which would be correct. A
From: Ryan Sun on 14 Apr 2010 10:45 Maybe this one works? array_diff(array_unique($array1 + $array2), array_intersect($array1, $array2)) On Wed, Apr 14, 2010 at 4:39 AM, Ashley Sheridan <ash(a)ashleysheridan.co.uk> wrote: > On Tue, 2010-04-13 at 23:01 -0600, Ashley M. Kirchner wrote: > >> I have the following scenario: >> >> >> >> $array1 = array("12", "34", "56", "78", "90"); >> >> $array2 = array("12", "23", "56", "78", "89"); >> >> >> >> $result = array_diff($array1, $array2); >> >> >> >> print_r($result); >> >> >> >> >> >> This returns: >> >> >> >> Array >> >> ( >> >> [1] => 34 >> >> [4] => 90 >> >> ) >> >> >> >> >> >> However what I really want is a two-way comparison. I want elements that >> don't exist in either to be returned: >> >> >> >> 34 and 90 because they don't exist in $array2, AND 23 and 89 because they >> don't exist in $array1. So, is that a two step process of first doing an >> array_diff($array1, $array2) then reverse it by doing array_diff($array2, >> $array1) and merge/unique the results? Any caveats with that? >> >> >> >> $array1 = array("12", "34", "56", "78", "90"); >> >> $array2 = array("12", "23", "56", "78", "89"); >> >> >> >> $diff1 = array_diff($array1, $array2); >> >> $diff2 = array_diff($array2, $array1); >> >> >> >> $result = array_unique(array_merge($diff1, $diff2)); >> >> >> >> print_r($result); >> >> >> >> >> >> -- A >> > > > I don't see any problems with doing it that way. This will only work as > you intended if both arrays have the same number of elements I believe, > otherwise you might end up with a situation where your final array has > duplicates of the same number: > > $array1 = $array(1, 2, 3, 4, 5, 6); > $array2 = $aray(1, 3, 2, 5); > > Thanks, > Ash > http://www.ashleysheridan.co.uk > > >
From: "Ashley M. Kirchner" on 14 Apr 2010 11:37 No because that only does a one-way comparison. It only tells me what's missing from $array2. I need it from both arrays. That's why I'm comparing 1 versus 2, then 2 versus 1, and then doing a merge/unique on the result. $array1 = array(1, 2, 3, 4, 5, 6); $array2 = array(1, 3, 2, 8, 9); $result = array_diff(array_unique($array1 + $array2), array_intersect($array1, $array2)); => (4, 5, 6) Versus: $array1 = array(1, 2, 3, 4, 5, 6); $array2 = array(1, 3, 2, 8, 9); $diff1 = array_diff($array1, $array2); $diff2 = array_diff($array2, $array1); $result = array_unique(array_merge($diff1, $diff2)); => (4, 5, 6, 8, 9) This second $result is what I want. So far I haven't noticed any problems doing it this way ... yet. I'm sure someone will tell me otherwise. Ash > -----Original Message----- > From: Ryan Sun [mailto:ryansun81(a)gmail.com] > Sent: Wednesday, April 14, 2010 8:45 AM > To: ash(a)ashleysheridan.co.uk > Cc: Ashley M. Kirchner; php-general(a)lists.php.net > Subject: Re: [PHP] Array differences > > Maybe this one works? > array_diff(array_unique($array1 + $array2), array_intersect($array1, > $array2)) > > On Wed, Apr 14, 2010 at 4:39 AM, Ashley Sheridan > <ash(a)ashleysheridan.co.uk> wrote: > > On Tue, 2010-04-13 at 23:01 -0600, Ashley M. Kirchner wrote: > > > >> I have the following scenario: > >> > >> > >> > >> $array1 = array("12", "34", "56", "78", "90"); > >> > >> $array2 = array("12", "23", "56", "78", "89"); > >> > >> > >> > >> $result = array_diff($array1, $array2); > >> > >> > >> > >> print_r($result); > >> > >> > >> > >> > >> > >> This returns: > >> > >> > >> > >> Array > >> > >> ( > >> > >> [1] => 34 > >> > >> [4] => 90 > >> > >> ) > >> > >> > >> > >> > >> > >> However what I really want is a two-way comparison. I want elements > that > >> don't exist in either to be returned: > >> > >> > >> > >> 34 and 90 because they don't exist in $array2, AND 23 and 89 because > they > >> don't exist in $array1. So, is that a two step process of first > doing an > >> array_diff($array1, $array2) then reverse it by doing > array_diff($array2, > >> $array1) and merge/unique the results? Any caveats with that? > >> > >> > >> > >> $array1 = array("12", "34", "56", "78", "90"); > >> > >> $array2 = array("12", "23", "56", "78", "89"); > >> > >> > >> > >> $diff1 = array_diff($array1, $array2); > >> > >> $diff2 = array_diff($array2, $array1); > >> > >> > >> > >> $result = array_unique(array_merge($diff1, $diff2)); > >> > >> > >> > >> print_r($result); > >> > >> > >> > >> > >> > >> -- A > >> > > > > > > I don't see any problems with doing it that way. This will only work > as > > you intended if both arrays have the same number of elements I > believe, > > otherwise you might end up with a situation where your final array > has > > duplicates of the same number: > > > > $array1 = $array(1, 2, 3, 4, 5, 6); > > $array2 = $aray(1, 3, 2, 5); > > > > Thanks, > > Ash > > http://www.ashleysheridan.co.uk > > > > > >
From: lala on 14 Apr 2010 12:14 Ashley M. Kirchner wrote: > > $array1 = array(1, 2, 3, 4, 5, 6); > $array2 = array(1, 3, 2, 8, 9); > $diff1 = array_diff($array1, $array2); > $diff2 = array_diff($array2, $array1); > $result = array_unique(array_merge($diff1, $diff2)); > > => (4, 5, 6, 8, 9) Hi Ash, Isn't the array_unique() unnecessary? Mike
From: "Ashley M. Kirchner" on 14 Apr 2010 12:20 > -----Original Message----- > From: lala [mailto:lala(a)mail.theorb.net] > Sent: Wednesday, April 14, 2010 10:15 AM > To: Ashley M. Kirchner > Cc: php-general(a)lists.php.net > Subject: Re: [PHP] Array differences > > Ashley M. Kirchner wrote: > > > > $array1 = array(1, 2, 3, 4, 5, 6); > > $array2 = array(1, 3, 2, 8, 9); > > $diff1 = array_diff($array1, $array2); > > $diff2 = array_diff($array2, $array1); > > $result = array_unique(array_merge($diff1, $diff2)); > > > > => (4, 5, 6, 8, 9) > > Hi Ash, > > Isn't the array_unique() unnecessary? > > Mike Thinking about it, it should be unnecessary, but at the same time I want to absolutely sure that I get unique values out of the two diffs. Ash
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