- preg_replace: documentation ( source)
<?php
$regex = '#<tag foo="bar">([\w\s]+[^\s]+)</tag>#';
echo preg_replace($regex, '\1', '<tag foo="bar">Jacopo Nuzzi</tag>'). " $\n";
echo preg_replace($regex, '\1', '<tag foo="bar">Jacopo Nuzzi </tag>'). " $\n";
echo preg_replace($regex, '\1', '<tag foo="bar">Jacopo </tag>'). " $\n";
echo preg_replace($regex, '\1', '<tag foo="bar">Jacopo</tag>'). " $\n";