AS3+PHP+MySQL : home-made online chat not always reactive

[sardarji]

I coded some kind of online chat system with a Flash (AS3) client that sends and retrieves data from a PHP script that communicates with a MySQL database.It works well, except for the fact that occasionally, my client doesn't get one of the new chat lines even though they are correctly registered in the database.Here is the basic logic behind it : every user has an entry in the database, and each of those entries has a lastChatCheck BigInt(16) variable.When a user types and sends a chat line, the client sends it to a PHP script, where it is stored in the database, along with the date it was stored at (it is also a BigInt(16) ).The flash client checks every 250 milliseconds through a getter PHP script for every chat line where (line's date>user's lastChatCheck), then sets the user's lastChatCheck to the last retrieved line's date. (Please tell me if this is confusing or poorly explained.)I am positive that the code I wrote to send a new line is correct, as everything I send gets correctly stored in the database.The (simplified) PHP code for getting the chat lines is like so :\[code\]$result=mysql_query('SELECT lastChatCheck FROM players WHERE id='.$id);while ($row=mysql_fetch_array($result)){$lastChatCheck=$row['lastChatCheck'];}$output='';$chatDate=0;$result=mysql_query('SELECT * FROM chat WHERE date>'.$lastChatCheck);while ($row=mysql_fetch_array($result)){$chatSayer=$row['sayer'];$chatText=$row['text'];$chatDate=$row['date'];$result2=mysql_query('SELECT name FROM players WHERE id='.$chatSayer);while ($row2=mysql_fetch_array($result2)){$output.=$row2['name'].' : '.$row['text'].'<br>';//(in reality, $output is formatted as an XML object)}}if ($chatDate!=0) mysql_query('UPDATE players SET lastChatCheck='.$chatDate.' WHERE id='.$id);\[/code\]Is there any logical reason why this would skip some of the recent chat lines ? Is there any way I can fix this ?