Question

I feel like I’ve done something very silly, but I can’t work out what it is.
I’m running through an array of arrays generated by fgetcsv(). What I want is to split the array in two at the spot where the value in one line differs from the one in the next.
This code results in $first holding all but one of the arrays, and $second holding the last – completely ignoring the string comparison. strcmp() results in the same thing.

$csv = array();
$file = fopen('A.csv', 'r');
while (($result = fgetcsv($file)) !== false)
{
    $csv[] = $result;
}
fclose($file);

array_shift($csv); //gets rid of the CSV headers
$rows = count($csv);

for ($i = 0; $i <= $rows; $i++){
    if ($csv[$i][1] != $csv[$i+1][1]){
        $first = array_slice($csv, 0, $i);
        $second = array_slice($csv, $i);
    }
}

Here’s an example of the CSV file:

NAME,MATCHNAME,CHROMOSOME,START LOCATION,END LOCATION,CENTIMORGANS,MATCHING SNPS
A,person_one,2,20945970,23287731,2.48,500
A,person_one,2,233444593,234432885,1.56,500
A,person_one,4,99184637,100861136,1.24,500
A,person_two,1,154990798,157871980,2.8,700 //Here's where the new array should start
A,person_two,1,67136078,70785393,2.28,800

EDIT: My expected $first for this example would be:

Array
(
[0] => Array
    (
        [0] => A
        [1] => person_one
        [2] => 2
        [3] => 20945970
        [4] => 23287731
        [5] => 2.48
        [6] => 500
    )

[1] => Array
    (
        [0] => A
        [1] => person_one
        [2] => 2
        [3] => 233444593
        [4] => 234432885
        [5] => 1.56
        [6] => 500
    )

[2] => Array
    (
        [0] => A
        [1] => person_one
        [2] => 4
        [3] => 99184637
        [4] => 100861136
        [5] => 1.24
        [6] => 500
    )
)

And my expected $second would be:

Array
(
[0] => Array
    (
        [0] => A
        [1] => person_two
        [2] => 1
        [3] => 154990798
        [4] => 157871980
        [5] => 2.8
        [6] => 700
    )

[1] => Array
    (
        [0] => A
        [1] => person_two
        [2] => 1
        [3] => 67136078
        [4] => 70785393
        [5] => 2.28
        [6] => 800
    )
)

Answer 1

It is doing what you want, but when it gets to the last iteration, it compares whatever’s in the last line with null, so it overwrites $first and $second.

Try adding break; after the assignments to break out of the loop when the condition is met.