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Abbrevia profile image Claudio Fior
Claudio Fior for Abbrevia

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Data in fixed fields text files

#text #php #datastructure

I have to read and write data from a fixed fields text file.
What is a it? It'a mess like this.

Fixed fields text file

The data organized based on the character position:
1 - 11 Packet ID
12 - 11 Anagraph ID
23 - 10 Submission date
and so on.

How can I read the data in PHP?

First, ugly solution: use substr to read

 $identificativo_pacchetto = substr($line,0,11); $identificativo_mandante = substr($line,11,11); $data_affido = substr($line,22,10); ...
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and str_pad to write

 $line = str_pad($identificativo_pacchetto,11); $line .= str_pad($identificativo_mandante,11); $line .= str_pad($data_affido,10); ...
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It'a nightmare!!!

Lets'try with unpack and pack command.

One line of code to read.

$data =unpack('A11identificativo_pacchetto/A11identificativo_mandante/A10data_affido',$line));
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and data is an array like this

{ "identificativo_pacchetto":"1", "identificativo_mandante":"52301", "data_affido":"19-11-2021" }
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One line of code to write

$data = ['1','52301','19-11-2021']; $line =pack('A11A11A10',...$data));
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The is no need to pad the values.
Note that the are no filed names (eg . identificativo_pacchetto) and no separators (/).

I put all together defining the structure in an array.

$def = [ 'A11identificativo_pacchetto', 'A11identificativo_mandante', 'A10data_affido ]; $data = ['1','52301','19-11-2021']; $line = pack(implode('',preg_replace('/^(A\d+).*/','$1',$def)),...$data); $data = unpack(implode('/',$def),$line);
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More info:
PHP manual
PHP Cookbook
Stackoverflow

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