Best way to avoid duplicate entry into mysql database

First step would be to set a unique key on the table:

ALTER TABLE thetable ADD UNIQUE INDEX(pageid, name);

Then you have to decide what you want to do when there's a duplicate. Should you:

1. ignore it?

   INSERT IGNORE INTO thetable (pageid, name) VALUES (1, "foo"), (1, "foo");
   

2. Overwrite the previously entered record?

   INSERT INTO thetable (pageid, name, somefield)
   VALUES (1, "foo", "first")
   ON DUPLICATE KEY UPDATE (somefield = 'first')
   
   INSERT INTO thetable (pageid, name, somefield)
   VALUES (1, "foo", "second")
   ON DUPLICATE KEY UPDATE (somefield = 'second')
   

3. Update some counter?

   INSERT INTO thetable (pageid, name)
   VALUES (1, "foo"), (1, "foo")
   ON DUPLICATE KEY UPDATE (pagecount = pagecount + 1)
   

You can also ignore the error with mysql: INSERT IGNORE INTO TABLE ... it will ignore the key error, skip over that insert and move on to the next.

From a mysql point you can do

alter table YOURTABLE add unique index(pageId, name);

If your wording is correct and you want to do it from php you can do

$already_done = array();
foreach ($records as $record)
{
   $unique_hash = md5($record['name'].$record['pageId']);
   if (!in_array($unique_hash, $already_done))
   {
      $already_done[] = $unique_hash;
      // sql insert here
   }
}

either way those should do you just fine.