- explode: documentation ( source)
<?php
$sometext = "Some text **that is bold!** and some other text";
$string = explode('**', $sometext);
$newStr = '';
for ($i = 0; $i < count($string); ++$i) {
if ($i % 2 == 0 || $i == 0)
$newStr .= $newStr[$i]."<b>";
else
$newStr .= $newStr[$i]."</b>" ;
}
echo $newStr;