Código PHP:
function getFilename( $file, $extension = true ) {
return ($extension || false === $dot = strrpos( basename( $file ), '"' ))
? basename( $file ) : substr( basename( $file ), 0, $dot );
}
$cadena = '<IMG alt="" hspace=0 src="dominio.com/imagen/pruebaas.jpg" align=baseline border=0>';
$new = strrchr($cadena,'/');
echo getFilename( $new, false );