Puoi fare cosi.

codice:
<?php
$pattern = '~<br/>$~msi';
$testo   = 'dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz<br/>';
print htmlentities($testo);
print "<br/>";
$testo2  = preg_replace($pattern,'',$testo);
print htmlentities($testo2);

codice:
dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz<br/>
dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz<br/>dkzdz