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<!DOCTYPE html> <html> <body> <?php $a1=array("a"=>"red","b"=>"green","c"=>"blue"); $a2=array("c"=>"yellow","d"=>"black","e"=>"brown"); $a3=array("f"=>"green","c"=>"purple","g"=>"red"); $result=array_intersect_key($a1,$a2,$a3); print_r($result); ?> </body> </html>