libraries/tbs/plugins/tbs_plugin_opentbs.php
function ReplaceInnerSrc($new) {
		$len = $this->GetInnerLen();
		if ($len===false) return false;
		$this->Txt = substr_replace($this->Txt, $new, $this->pST_PosEnd + 1, $len);
		$this->PosEnd += strlen($new) - $len;
		$this->pET_PosBeg += strlen($new) - $len;
	}
function ReplaceInnerSrc($new) {
		$len = $this->GetInnerLen();
		if ($len===false) return false;
		$this->Txt = substr_replace($this->Txt, $new, $this->pST_PosEnd + 1, $len);
		$this->PosEnd += strlen($new) - $len;
		$this->pET_PosBeg += strlen($new) - $len;
	}
Assume FindEndTag() is previsouly called.