<?php

// uncomment the appropiate linebreak
define(LINEBREAK, '<br>');
//define(LINEBREAK, "\r");
//define(LINEBREAK, "\n");


// this sets maximum lines per sig
$maxlines = 4;

// splits line breaks into arrays
$pieces = strpos($string, LINEBREAK) ? explode(LINEBREAK, $string) : $string;

// counts line breaks
$numOfBreaks = count($pieces);

// defines maxlines appropiately
$maxlines = $numOfBreaks - $maxlines;

// removes extra lines
for ($i=0;$i<$maxlines;$i++){
  array_pop($pieces);
}

// places arrays back together
$whole = implode($pieces, LINEBREAK);

//echos new signature
print_r($whole);