PHP_XLSwriter array output - php

Question

I'm working with a bit of php code called PHP_XLSWriter. It accepts an input, then outputs it to an Excel sheet.
Their example.php page does exactly what I want, and in it, there's a bit of code that determines what specifically gets exported:
$data1 = array(
array('2003','1','-50.5','2010-01-01 23:00:00'),
array('2003','=B2', '23.5','2010-01-01 00:00:00'),
);
I haven't written arrays like this exactly in the past, but I've passed my own array into this page through AJAX from a separate page. I'm not sure if it's important how I did this, but I'm happy to paste in that code if it is.
When I try to execute the page using MY array, the page fails and my console is full of intelligible text.
I can't figure out why this is as the var_dump of our two arrays are exactly the same.
the original var_dump($data1);
array(2) {
[0]=>
array(4) {
[0]=>
string(4) "2003"
[1]=>
string(1) "1"
[2]=>
string(5) "-50.5"
[3]=>
string(19) "2010-01-01 23:00:00"
}
[1]=>
array(4) {
[0]=>
string(4) "2003"
[1]=>
string(3) "=B2"
[2]=>
string(4) "23.5"
[3]=>
string(19) "2010-01-01 00:00:00"
}
}
the var_dump() when I set $data1 equal to the array I've imported:
array(2) {
[0]=>
array(4) {
[0]=>
string(6) "blah"
[1]=>
string(12) "two"
[2]=>
string(6) "0.0160"
[3]=>
string(6) "0.0173"
}
[1]=>
array(4) {
[0]=>
string(3) "blah"
[1]=>
string(14) "three"
[2]=>
string(6) "0.0085"
[3]=>
string(6) "0.0095"
}
}
and echo gettype($data1); outputs array for both of the strings.
What might I be doing to cause this to break? I'm positive it has something to do with my array, as all else held equal, the code works.