File_MARC_Reference

File_MARC_Reference is an extension to the famous MARC parser for PHP File_MARC. With File_MARC_Reference you can use MARCspec as an unified way to access MARC data. Besides it simplifies File_MARC a lot.

Installation

Installation can be done by using Composer. Just run

composer require ck/file_marc_reference

Usage

First require autoload.php

<?php
require("vendor/autoload.php");

Reading MARC 21 data from a file or string stays the same (see File_MARC - Reading MARC data):

// Retrieve a set of MARC records from a file
$records = new File_MARC('data.mrc');

// Iterate through the retrieved records
while ($record = $records->next())
{
 //...
}

Now if you want to reference data using a MARCspec you have to initialize a new File_MARC_Reference:

// Retrieve a set of MARC records from a file
$records = new File_MARC('data.mrc');

// Iterate through the retrieved records
while ($record = $records->next())
{
    $reference = new File_MARC_Reference('245$a',$record);
}

After you referenced the data three public attributes are available:

$reference = new File_MARC_Reference('245$a',$record);

// attribute data
$subfield = $reference->data[0];
print get_class($subfield);               // File_MARC_Subfield
print $subfield->getCode();               // a

// attribute content
print $reference->content[0];             // prints content of subfield a of field 245

// attribute cache
$field = $reference->cache['245'][0];
print get_class($field);                  // File_MARC_Data_Field
$subfield = $reference->cache['245$a'];
print get_class($subfield);               // File_MARC_Subfield

Let's see how we check dependencies with File_MARC if you have a task like: Reference to content of subfield "a" of field 306 if character with index position "0" of field 007 is either "m", "s" or "v".

Instead of writing ...

$fields_007 = $record->getFields('007');

$field_306 = $record->getField('306');

$subfields_a = false;

foreach($fields_007 as $field_007)
{
    $firstChar = substr($field_007->getData(),0,1);
    
    if(strpbrk($firstChar,"msv"))
    {
        $subfields_a = $field_306->getSubfields('a');
        break;
    }
}

if($subfields_a)
{
    foreach($subfields_a as $subfield_a)
    {
        echo $subfield_a->getData()."\n";
    }
}

... the same task with File_MARC_Reference:

    $reference = new File_MARC_Reference('306$a{007/0=\m|007/0=\s|007/0=\v}',$record);
    
    foreach($reference->content as $subfield_a)
    {
        echo $subfield_a."\n";
    }
    
    // interested in field 007? No problem!
    print get_class($reference->cache['007'][0]);       // File_MARC_Control_Field
    print $reference->cache['007/0'][0];                // prints the first char of first 007 field
    print $reference->cache['007/0'][1];                // prints the first char of second 007 field