Collision between shared data
<p>This is a common problem about sharing data.</p>

<p>As i am building a system that allow user share their mailing list to their colleague.</p>

<p>I suspect there is a problem when userA open the page , 
userB open the same page and edit the data, 
after that user A edit the data and submit and the changes of userB will be cancel.</p>

<p>As i am using PHP , is their any way to prevent this kind of error???  Thank you.|</p>

<p>Are there any coding example provided in php /jquery??? Thanks a lot</p>
