PHP用空格分割文本为数组的方法

1 字段1 字段2
2 字段1 字段2
3 字段1 字段2
4 字段1 字段2

<?php
$file = fopen("text.txt", "r") or exit("Unable to open file!");
while(!feof($file))
{
$arr = split(' ' , fgets($file));
print_r($arr);
}
fclose($file);
?>

Array
(
[0] => 1
[1] => 字段1
[2] => 字段2

)
Array
(
[0] => 2
[1] => 字段1
[2] => 字段2

)
Array
(
[0] => 3
[1] => 字段1
[2] => 字段2

)
Array
(
[0] => 4
[1] => 字段1
[2] => 字段2
)