explode('/', $buffer[$i]) 

<?php
header('Content-Type: text/plain');

// Missing database connection

$fh = fopen('sample-data.txt', 'r');
while (!feof($fh))
{
    // Loads the next line into an array
    $csv = fgetcsv($fh, 8192);
    
    // Splits the date string into date parts
    $dp = explode('/', $csv[3]);
    
    // Rearranges the date parts and adds dashes
    $csv[3] = "{$dp[2]}-{$dp[0]}-{$dp[1]}";
    
    // Builds the query, adding a comma between each value and single-quotes around string values
    $query = "INSERT INTO `anii_cp1`.`student` (`student_ID`, `course_code`, `GPA`, `commencement_date`, `process_category`) "
           . "VALUES ({$csv[0]}, {$csv[1]}, {$csv[2]}, '{$csv[3]}', '{$csv[4]}')";
    
    if (false === mysql_query($query))
        echo 'Query failed: ';
    
    echo $query . "\n";
}
fclose($fh);
?>

$csv[3] = "{$dp[2]}-{$dp[1]}-{$dp[0]}";