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Home Backend Development PHP Tutorial PHP快速按行讀取CSV大文件的封裝類分享(也適用于其它超大文本文_PHP

PHP快速按行讀取CSV大文件的封裝類分享(也適用于其它超大文本文_PHP

Jun 01, 2016 am 11:54 AM
csv php large files

CSV大文件的讀取已經(jīng)在前面講述過了(PHP按行讀取、處理較大CSV文件的代碼實(shí)例),但是如何快速完整的操作大文件仍然還存在一些問題。

1、如何快速獲取CSV大文件的總行數(shù)?

辦法一:直接獲取文件內(nèi)容,使用換行符進(jìn)行拆分得出總行數(shù),這種辦法對(duì)小文件可行,處理大文件時(shí)不可行;
辦法二:使用fgets一行一行遍歷,得出總行數(shù),這種辦法比辦法一好一些,但大文件仍有超時(shí)的可能;
辦法三:借助SplFileObject類,直接將指針定位到文件末尾,通過SplFileObject::key方法獲取總行數(shù),這種辦法可行,且高效。

具體實(shí)現(xiàn)方法:
復(fù)制代碼 代碼如下:
$csv_file = 'path/bigfile.csv';
$spl_object = new SplFileObject($csv_file, 'rb');
$spl_object->seek(filesize($csv_file));
echo $spl_object->key();

2、如何快速獲取CSV大文件的數(shù)據(jù)?

仍然使用PHP的SplFileObject類,通過seek方法實(shí)現(xiàn)快速定位。
復(fù)制代碼 代碼如下:
$csv_file = 'path/bigfile.csv';
$start = 100000;??// 從第100000行開始讀取
$num = 100;????// 讀取100行
$data = array();
$spl_object = new SplFileObject($csv_file, 'rb');
$spl_object->seek($start);
while ($num-- && !$spl_object->eof()) {
?$data[] = $spl_object->fgetcsv();
?$spl_object->next();
}
print_r($data);

3、綜合上面兩點(diǎn),整理成一個(gè)csv文件讀取的類:
復(fù)制代碼 代碼如下:
class CsvReader {
?private $csv_file;
?private $spl_object = null;
?private $error;

?public function __construct($csv_file = '') {
??if($csv_file && file_exists($csv_file)) {
???$this->csv_file = $csv_file;
??}
?}

?public function set_csv_file($csv_file) {
??if(!$csv_file || !file_exists($csv_file)) {
???$this->error = 'File invalid';
???return false;
??}
??$this->csv_file = $csv_file;
??$this->spl_object = null;
?}

?public function get_csv_file() {
??return $this->csv_file;
?}

?private function _file_valid($file = '') {
??$file = $file ? $file : $this->csv_file;
??if(!$file || !file_exists($file)) {
???return false;
??}
??if(!is_readable($file)) {
???return false;
??}
??return true;
?}

?private function _open_file() {
??if(!$this->_file_valid()) {
???$this->error = 'File invalid';
???return false;
??}
??if($this->spl_object == null) {
???$this->spl_object = new SplFileObject($this->csv_file, 'rb');
??}
??return true;
?}

?public function get_data($length = 0, $start = 0) {
??if(!$this->_open_file()) {
???return false;
??}
??$length = $length ? $length : $this->get_lines();
??$start = $start - 1;
??$start = ($start ??$data = array();
??$this->spl_object->seek($start);
??while ($length-- && !$this->spl_object->eof()) {
???$data[] = $this->spl_object->fgetcsv();
???$this->spl_object->next();
??}
??return $data;
?}

?public function get_lines() {
??if(!$this->_open_file()) {
???return false;
??}
??$this->spl_object->seek(filesize($this->csv_file));
??return $this->spl_object->key();
?}

?public function get_error() {
??return $this->error;
?}
}
調(diào)用方法如下:
復(fù)制代碼 代碼如下:
include('CsvReader.class.php');

$csv_file = 'path/bigfile.csv';

$csvreader = new CsvReader($csv_file);

$line_number = $csvreader->get_lines();

$data = $csvreader->get_data(10);

?

echo $line_number, chr(10);

print_r($data);


其實(shí),上述CsvReader類并不只針對(duì)CSV大文件,對(duì)于其他文本類型的大文件或超大文件同樣可用,前提是將類中fgetcsv方法稍加改動(dòng)為current即可。

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