Tabular Data Reader Common API

Introduced in version 9.6 the League\Csv\TabularDataReader interface provides a common API to works with tabular data like structure. Once implemented, it can be used to work with HTML tables, simple RDBMS tables, CSV document and so forth. A tabular data is made of:

• a collection of similar records (preferably consistent in their size);
• an optional header with unique values;

A record MUST* be a simple PHP array (the array MUST NOT be nested) which can be

• a list;
• or an associative array;

A header is a record which MUST contain unique string values.

A good example of what you can achieve can be seen with the following snippet

use League\Csv\Reader;

$records = Reader::createFromPath('/path/to/file.csv')
    ->filter(fn (array $record): bool => false !== filter_var($record[2] ?? '', FILTER_VALIDATE_EMAIL))
    ->select(1, 4, 5)
    ->slice(3, 5)
    ->each(function (array $record) {
        //do something meaningful with the found records
    });

Once you created a TabularDataReader implementing instance, here we are using the Reader you will be able to filter, slice and select part of your data to finally access it using the getRecords method. You will also be able to process the instance using a Statement object. All these methods are part of the TabularDataReader contract. In general, TabularDataReader are immutable, meaning every TabularDataReader method returns an entirely new TabularDataReader instance leaving your source data unchanged.

Available methods

While the TabularDataReader is not a fully fledged collection instance it still exposes a lots of methods that fall into the category of records collection manipulations. Because chaining is at the core of most of its methods you can be sure that each manipulation returns a new instance preserving your original data.

Countable, IteratorAggregate

Any TabularDataReader instance implements the Countable and the IteratorAggregate interface. It means that at any given time you can access the number of elements that are included in the instance as well as iterate over all the record using the foreach structure.

use League\Csv\Reader;

$reader = Reader::createFromPath('/path/to/my/file.csv');
count($reader); //returns 4
foreach ($reader as $offset => $record) {
    //iterates over the 4 records.
}

Selecting records

getHeader

The getHeader returns the header associated with the current object. If the current object has no header, it will return the empty array.

use League\Csv\Reader;

$reader = Reader::createFromPath('/path/to/my/file.csv');
$reader->getHeader(); //is empty because no header information was given

getRecords

Added in version 9.6.0 for ResultSet.

full mapper usage was completed in version 9.12 for Reader and ResultSet.

The getRecords enables iterating over all records from the current object. If the optional $header argument is given, it will be used as a mapper on the record and will update the record header and the value position.

use League\Csv\Reader;

$csv = <<<CSV
Abel,14,M,2004
Abiga,6,F,2004
Aboubacar,8,M,2004
Aboubakar,6,M,2004
CSV;

$reader = Reader::createFromString($csv);
$resultSet = Statement::create()->process($reader);
$records = $resultSet->getRecords([3 => 'Year', 0 => 'Firstname', 4 => 'Yolo']);
var_dump([...$records][0]);
//returns something like this
// array:4 [
//     "Year" => "2004",
//     "Firstname" => "Abel",
//     "Yolo" => null,
//  ]

The argument now links the records column offset to a specific column name. In other words this means that the array key which MUST be a positive integer or 0 will correspond to the CSV column offset and its value will represent its header value.

This means that you can re-arrange the column order as well as removing or adding column to the returned iterator. Added column will only contain the null value.

If the header record contains non-unique string values, a Exception exception is triggered.

getRecordsAsObject

getObjects is deprecated in favor of getRecordsAsObject to make the public API more consistent.

getObjects Added in version 9.12.0 for Reader and ResultSet.

getRecordsAsObject Added in version 9.15.0 for Reader and ResultSet.

If you prefer working with objects instead of arrays it is possible to deserialize your CSV document using the getRecordsAsObject method. This method will convert each CSV record into your specified class instances.

$csv = Reader::createFromString($document);
$csv->setHeaderOffset(0);
foreach ($csv->getRecordsAsObject(ClimaticRecord::class) as $instance) {
    // each $instance entry will be an instance of the Weather class;
}

The getRecordsAsObject method can take an optional $header argument which is the same mapper argument as the one use with the getRecords method.

You can get more info on how to configure your class to enable this feature by visiting the record mapping documentation page

value, first, nth, firstAsObject and nthAsObject

firstAsObject and nthAsObject were added in version 9.14.0 for Reader and ResultSet.

first and nth were added in version 9.9.0 for Reader and ResultSet.

value was added in version 9.12.0 for Reader and ResultSet.

You may access any record using its offset starting at 0 in the collection using the nth method. if no record is found, an empty array is returned.

use League\Csv\Reader;
use League\Csv\Statement;

$reader = Reader::createFromPath('/path/to/my/file.csv', 'r');
$reader->setHeaderOffset(0);

$stmt = Statement::create()
    ->offset(10)
    ->limit(12)
;
$result = $stmt->process($reader);
$result->nth(3);
// access the 4th record from the recordset (indexing starts at 0)
// will return something like this :
//
//   ['john', 'doe', 'john.doe@example.com']
//

$result->first();
$result->nth(0);
//returns the first matching record from the recordset or an empty record if none is found.

As an alias to nth, the first method returns the first record from the instance without the need of an argument.

If you are only interested in retrieving a specific value from a single row, you can use the value method. By default, it will return the first record item, but you are free to specify a specific column using the column name if the header is set and/or the column offset, If no column is found null is returned.

use League\Csv\Reader;
use League\Csv\Statement;

$reader = Reader::createFromPath('/path/to/my/file.csv', 'r');
$reader->setHeaderOffset(0);

$stmt = Statement::create()
    ->offset(10)
    ->limit(12)
;
$result = $stmt->process($reader);
$result->value(2);       //returns 'john.doe@example.com'
$result->value('email'); //returns 'john.doe@example.com'
$result->value('toto'); //returns null
$result->value(42); //returns null

The fetchOne method was deprecated in version 9.9.0. it is recommended to use the nth method instead.

firstAsObject and nthAsObject are counterpart of first and nth respectively but returns null or an instance of the specified object. The methods requires, in addition to the record offset, the class name and optionally a header mapper just like getRecordsAsObjects.

use League\Csv\Reader;
use League\Csv\Statement;

$csv = Reader::createFromPath('/path/to/my/file.csv', 'r');
$csv->setHeaderOffset(0);

$csv->nthAsObject(3, ClimaticRecord::class);
$csv->firstAsObject(OtherClimatRecord::class, [2 => 'observedOn', 1 => 'temparature', 0 => 'place']);

exists

Added in version 9.11.0 for Reader and ResultSet.

Tests for the existence of a record that satisfies a given predicate.

use League\Csv\Reader;
use League\Csv\Statement;

$reader = Reader::createFromPath('/path/to/my/file.csv', 'r');
$resultSet = Statement::create()->process($reader);

$exists = $resultSet->exists(fn (array $records) => in_array('twenty-five', $records, true));

//$exists returns true if at least one cell contains the word `twenty-five` otherwise returns false,

Selecting columns

fetchColumnByName

The fetchColumnByName returns an Iterator containing all the values of a single column specified by its header name if it exists.

$reader = Reader::createFromPath('/path/to/my/file.csv');
$reader->setHeaderOffset(0);
$records = Statement::create()->process($reader);
foreach ($records->fetchColumnByName('e-mail') as $value) {
    //$value is a string representing the value
    //of a given record for the selected column
    //$value may be equal to 'john.doe@example.com'
}

Added in version 9.8.0 for Reader and ResultSet.

fetchColumnByOffset

The fetchColumnByOffset returns an Iterator containing all the values of a single column specified by its header offset.

$reader = Reader::createFromPath('/path/to/my/file.csv');
$reader->setHeaderOffset(0);
$records = Statement::create()->process($reader);
foreach ($records->fetchColumnByOffset(3) as $value) {
    //$value is a string representing the value
    //of a given record for the selected column
    //$value may be equal to 'john.doe@example.com'
}

Added in version 9.8.0 for Reader and ResultSet.

fetchPairs

The fetchPairs method returns an Iterator of key-value pairs from two tabular data columns. The method expect 2 arguments, both can be:

• an integer which represents the column name index;
• a string representing the value of a column name;

These arguments behave exactly like the $columnIndex from ResultSet::fetchColumnByName and ResultSet::fetchColumnByOffset.

use League\Csv\Reader;
use League\Csv\Statement;

$str = <<<EOF
john,doe
jane,doe
foo,bar
sacha
EOF;

$reader = Reader::createFromString($str);
$records = Statement::create()->process($reader);

foreach ($records->fetchPairs() as $firstname => $lastname) {
    // - first iteration
    // $firstname -> 'john'
    // $lastname  -> 'doe'
    // - second iteration
    // $firstname -> 'jane'
    // $lastname  -> 'doe'
    // - third iteration
    // $firstname -> 'foo'
    // $lastname  -> 'bar'
    // - fourth iteration
    // $firstname -> 'sacha'
    // $lastname  -> null
}

Notes

• If no $offsetIndex is provided it defaults to 0;
• If no $valueIndex is provided it defaults to 1;
• If no cell is found corresponding to $offsetIndex the row is skipped;
• If no cell is found corresponding to $valueIndex the null value is used;

If the TabularDataReader contains column names and the submitted arguments are not found, an Exception exception is thrown.

Functional methods

each

Added in version 9.11.0 for Reader and ResultSet.

The each method iterates over the records in the tabular data collection and passes each record to a closure.

use League\Csv\Reader;
use League\Csv\Writer;

$writer = Writer::createFromString();
$reader = Reader::createFromPath('/path/to/my/file.csv', 'r');
$reader->each(function (array $record, int $offset) use ($writer) {
     if ($offset < 10) {
        return $writer->insertOne($record);
     }
     
     return false;
});

//$writer will contain at most 10 lines coming from the $reader document.
// the iteration stopped when the closure return false.

You may interrupt the iteration if the closure passed to each returns false.

reduce

Added in version 9.11.0 for Reader and ResultSet.

The reduce method reduces the tabular data structure to a single value, passing the result of each iteration into the subsequent iteration:

use League\Csv\Reader;
use League\Csv\ResultSet;

$reader = Reader::createFromPath('/path/to/my/file.csv', 'r');
$resultSet = ResultSet::createFromTabularDataReader($reader);

$nbTotalCells = $resultSet->reduce(fn (?int $carry, array $records) => ($carry ?? 0) + count($records));

//$records contains the total number of cells contains in the $resultSet

The closure is similar as the one used with array_reduce.

Collection methods

The following methods return all a new TabularDataReader instance. They effectively allow selecting a range of records or columns contained within the TabularDataReader schema.

filter

Returns all the elements of this collection for which your callback function returns true. The order and keys of the elements are preserved.

use League\Csv\Reader;

$reader = Reader::createFromPath('/path/to/my/file.csv', 'r');
$records = $reader->filter(fn (array $record): => 5 === count($record));

//$records is a ResultSet object with only records with 5 elements

Wraps the functionality of Statement::where.

Added in version 9.11.0 for Reader and ResultSet.

sorted

Sorts the CSV document while keeping the original keys.

use League\Csv\Reader;

$reader = Reader::createFromPath('/path/to/my/file.csv', 'r');
$records = $reader->sorted(fn (array $recordA, array $recordB) => $recordA['firstname'] <=> $recordB['firstname']);

//$records is a ResultSet containing the sorted CSV document. 
//The original $reader is not changed

Wraps the functionality of Statement::orderBy.

Added in version 9.11.0 for Reader and ResultSet.

slice

Extracts a slice of $length elements starting at position $offset from the Collection. If $length is -1 it returns all elements from $offset to the end of the Collection. Keys have to be preserved by this method. Calling this method will only return the selected slice and NOT change the elements contained in the collection slice is called on.

use League\Csv\Reader;
use League\Csv\Statement;

$reader = Reader::createFromPath('/path/to/my/file.csv', 'r');
$resultSet = Statement::create()->process($reader);

$records = $resultSet->slice(10, 25);

//$records is a TabularDataReader which contains up to 25 rows
//starting at the offset 10 (the eleventh rows)

Wraps the functionality of Statement::offset and Statement::limit.

Added in version 9.11.0 for Reader and ResultSet.

select

You may not always want to select all columns from the tabular data. Using the select method, you can specify which columns to use. The column can be specified by their name, if the instance getHeader returns a non-empty array, or you can default to using the column offset. You can even mix them both.

use League\Csv\Reader;

$reader = Reader::createFromPath('/path/to/my/file.csv')
    ->select(2, 5, 8);

//$reader is a new TabularDataReader with 3 columns

Added in version 9.12.0 for Reader and ResultSet.

Wraps the functionality of Statement::select.

mapHeader

Added in version 9.15.0 for Reader and ResultSet.

Wraps the functionality of Statement::process.

Complementary to the select method, the mapHeader method allows you to redefine the column header names and order and returns a new TabularDataReader. The submitted array argument act like the array from the Statement::process method but instead of returning a iterable structure of records it returns a new TabularDataReader with a new header.

$tabularData = $reader
    ->slice(0, 10)
    ->mapHeader([
        3 => 'Year',
        2 => 'Gender',
        0 => 'Firstname',
        1 => 'Count',
    ]);

//is equivalent to

$tabularData = Statement::create()
    ->offset(0)
    ->limit(10)
    ->process($reader, [
        3 => 'Year',
        2 => 'Gender',
        0 => 'Firstname',
        1 => 'Count',
    ]);
$tabularData->getHeader(); // returns ['Year', 'Gender', 'Firstname', 'Count'];

matching, matchingFirst, matchingFirstOrFail

The matching method allows selecting records, columns or cells from the tabular data reader that match the RFC7111 expression and returns a new collection containing these elements without preserving the keys. The method wraps the functionality of FragmentFinder::findAll. Conversely, matchingFirst wraps the functionality of FragmentFinder::findFirst and last but not least, FragmentFinder::findFirstOrFail behaviour is wrap inside the matchingFirstOrFail method.

use League\Csv\Reader;

$reader = Reader::createFromString($csv);

$reader->matching('row=3-1;4-6'); //returns an iterable containing all the TabularDataReader instance that are valid.
$reader->matchingFirst('row=3-1;4-6'); // will return 1 selected fragment as a TabularReaderData instance
$reader->matchingFirstOrFail('row=3-1;4-6'); // will throw

Wraps the functionality of FragmentFinder class.

Added in version 9.12.0 for Reader and ResultSet.

chunkBy

Added in version 9.15.0 for Reader and ResultSet.

If you are dealing with a large CSV and you want it to be split in smaller sizes for better handling you can use the chunkBy method which breaks the TabularDataReader into multiple, smaller instances with a given size. The last instance may contain fewer records because of the chunk size you have chosen.

use League\Csv\Reader;
use League\Csv\TabularDataReader;
use League\Csv\Writer;

$chunks = Reader::createFromPath('path/to/a/huge/file.csv')->chunkBy(1000);
foreach ($chunks as $chunk) {
 // $chunk is a small CSV of 1000 records or less
}