我看到了多个线程，讨论自动检测传入CSV的分隔符的最佳解决方案。其中大多数是长度在20-30行之间的函数，多个循环预先确定的分隔符列表，读取前5行并匹配计数e.t.c e.t.c
以下是一个示例
我刚刚实施了这个程序，并做了一些修改。工作出色。
然后我发现了以下代码：
private function DetectDelimiter($fh)
{
$data_1 = null;
$data_2 = null;
$delimiter = self::$delim_list['comma'];
foreach(self::$delim_list as $key=>$value)
{
$data_1 = fgetcsv($fh, 4096, $value);
$delimiter = sizeof($data_1) > sizeof($data_2) ? $key : $delimiter;
$data_2 = $data_1;
}
$this->SetDelimiter($delimiter);
return $delimiter;
}
在我看来，这似乎实现了相同的结果，其中$delim_list是一个分隔符数组，如下所示：
static protected $delim_list = array('tab'=>"'t",
'semicolon'=>";",
'pipe'=>"|",
'comma'=>",");
有人能解释为什么我不应该用这种更简单的方式来做吗？为什么在我看来，更复杂的解决方案似乎是公认的答案？
谢谢！
这个函数很优雅：）
/**
* @param string $csvFile Path to the CSV file
* @return string Delimiter
*/
public function detectDelimiter($csvFile)
{
$delimiters = [";" => 0, "," => 0, "'t" => 0, "|" => 0];
$handle = fopen($csvFile, "r");
$firstLine = fgets($handle);
fclose($handle);
foreach ($delimiters as $delimiter => &$count) {
$count = count(str_getcsv($firstLine, $delimiter));
}
return array_search(max($delimiters), $delimiters);
}
这些都不适用于我的用例。所以我做了一些小的修改。
/**
* @param string $filePath
* @param int $checkLines
* @return string
*/
public function getCsvDelimiter(string $filePath, int $checkLines = 3): string
{
$delimiters =[",", ";", "'t"];
$default =",";
$fileObject = new 'SplFileObject($filePath);
$results = [];
$counter = 0;
while ($fileObject->valid() && $counter <= $checkLines) {
$line = $fileObject->fgets();
foreach ($delimiters as $delimiter) {
$fields = explode($delimiter, $line);
$totalFields = count($fields);
if ($totalFields > 1) {
if (!empty($results[$delimiter])) {
$results[$delimiter] += $totalFields;
} else {
$results[$delimiter] = $totalFields;
}
}
}
$counter++;
}
if (!empty($results)) {
$results = array_keys($results, max($results));
return $results[0];
}
return $default;
}
固定版本。
在代码中，如果一个字符串有多个分隔符，则会得到错误的结果（例如：val；string，带逗号；val2；val3）。此外，如果文件有1行（行数<分隔符数）。
这里有一个固定的变体：
private function detectDelimiter($fh)
{
$delimiters = ["'t", ";", "|", ","];
$data_1 = null; $data_2 = null;
$delimiter = $delimiters[0];
foreach($delimiters as $d) {
$data_1 = fgetcsv($fh, 4096, $d);
if(sizeof($data_1) > sizeof($data_2)) {
$delimiter = $d;
$data_2 = $data_1;
}
rewind($fh);
}
return $delimiter;
}
通常，您无法检测文本文件的分隔符。如果有其他提示，您需要在检测中实现它们以确保安全。
所建议的方法的一个特殊问题是，它将计算文件不同行中的元素数量。假设你有一个这样的文件：
a;b;c;d
a b; c d
this|that;here|there
It's not ready, yet.; We have to wait for peter, paul, and mary.; They will know what to do
尽管这似乎用分号分隔，但您的方法将返回comma。
另一个（结合我在互联网上找到的许多答案构建而成：
/**
* Detects the delimiter of a CSV file (can be semicolon, comma or pipe) by trying every delimiter, then
* counting how many potential columns could be found with this delimiter and removing the delimiter from array of
* only one columns could be created (without a working limiter you'll always have "one" column: the entire row).
* The delimiter that created the most columns is returned.
*
* @param string $pathToCSVFile path to the CSV file
* @return string|null nullable delimiter
* @throws 'Exception
*/
public static function detectDelimiter(string $pathToCSVFile): ?string
{
$delimiters = [
';' => 0,
',' => 0,
"|" => 0,
];
$handle = fopen($pathToCSVFile, 'r');
$firstLine = fgets($handle);
fclose($handle);
foreach ($delimiters as $delimiterCharacter => $delimiterCount) {
$foundColumnsWithThisDelimiter = count(str_getcsv($firstLine, $delimiterCharacter));
if ($foundColumnsWithThisDelimiter > 1) {
$delimiters[$delimiterCharacter] = $foundColumnsWithThisDelimiter;
}else {
unset($delimiters[$delimiterCharacter]);
}
}
if (!empty($delimiters)) {
return array_search(max($delimiters), $delimiters);
} else {
throw new 'Exception('The CSV delimiter could not been found. Should be semicolon, comma or pipe!');
}
}
以及相应的单元测试（您必须添加自定义的test.csv文件）：
/**
* Test the delimiter detector
*
* @test
*/
public function testDetectDelimiter()
{
$this->assertEquals(',', Helper::detectDelimiter('test1.csv'));
$this->assertEquals(';', Helper::detectDelimiter('test-csv-with-semicolon-delimiter.csv'));
$this->assertEquals('|', Helper::detectDelimiter('test-csv-with-pipe-delimiter.csv'));
$this->expectExceptionMessage('The CSV delimiter could not been found. Should be semicolon, comma or pipe!');
Helper::detectDelimiter('test-csv-with-failing-delimiter.csv');
}
好的，这个解析CSV的一行（通常是第一行），如果可能有多个delimeter或没有匹配的delimeter，则抛出Exception。根据这一点，看起来你想要测试的delimeter不在引用的字符串中或转义了。
public function getDelimiter(string $content, $throwExceptionOnNonUnique = true, $expectSingleColumn = false): string
{
// Would be cleaner if you pass the delimiters from outside
// as also the order matters in the special case you've got something like "a,b;c"
// and you don't throw the exception - then the first match is preferred
// But for StackOverflow I put them inside
$delimiters = ["'t", ";", "|", ","];
$result = ',';
$maxCount = 0;
foreach ($delimiters as $delimiter) {
// Impress your code reviewer by some badass regex ;)
$pattern = "/(?<!''')(?:''''''')*(?!'B'"[^'''"]*)''" . $delimiter . "(?![^'"]*'''"'B)/";
$amount = preg_match_all($pattern, $content);
if ($maxCount > 0 && $amount > 0 && $throwExceptionOnNonUnique) {
$msg = 'Identifier is not clear: "' . $result . '" and "' . $delimiter . '" are possible';
throw new 'Exception($msg);
}
if ($amount > $maxCount) {
$maxCount = $amount;
$result = $delimiter;
}
}
// If nothing matches and you don't expect that just the CSV just
// consists of one single column without a delimeter at the end
if ($maxCount === 0 && !$expectSingleColumn) {
throw new 'Exception('Unknown delimiter');
}
return $result;
}
附言：也是单元测试，但我不想在这里粘贴100多行测试；）
这是最短的版本，通过使用SplFileObject类和方法getCsvControl并使用数组取消引用来检测CSV分隔符。
不过有一个问题，下面的函数只有在使用setCsvControl（）函数手动设置分隔符的情况下才有效，否则，请使用评分最高的答案之一。
// SplFileObject::getCsvControl — Get the delimiter, enclosure and escape character for CSV
function detectDelimiter($csvFile){
if(!file_exists($csvFile) || !is_readable($csvFile)){
return false;
}
$file = new SplFileObject($csvFile);
return $file->getCsvControl()[0];
}