Use PHP Document Object Model:
<?php
$str = '<h1>T1</h1>Lorem ipsum.<h1>T2</h1>The quick red fox...<h1>T3</h1>... jumps over the lazy brown FROG';
$DOM = new DOMDocument;
$DOM->loadHTML($str);
//get all H1
$items = $DOM->getElementsByTagName('h1');
//display all H1 text
for ($i = 0; $i < $items->length; $i++)
echo $items->item($i)->nodeValue . "<br/>";
?>
This outputs as:
T1
T2
T3
[EDIT]: After OP Clarification:
If you want the content like Lorem ipsum. etc, you can directly use this regex:
<?php
$str = '<h1>T1</h1>Lorem ipsum.<h1>T2</h1>The quick red fox...<h1>T3</h1>... jumps over the lazy brown FROG';
echo preg_replace("#<h1.*?>.*?</h1>#", "", $str);
?>
this outputs:
Lorem ipsum.The quick red fox...... jumps over the lazy brown FROG
