Question

I need to display a plain-text file that contains two-space tab’d columns of data in a web page.

What I did was to use PHP to read the text file and print it out between <pre> tags to use a monospace font as so:

<pre>
<?php
  $fn="data.txt";
  $fi=fopen($fn, "r");
  $fc=fread($fi, filesize($fn));         //open and read text file
  fclose($fi);
  $fc=str_replace("\t", "  ", $fc);      //replace tabs with two spaces
  print($fc);                            //print data between PRE tags
?>
</pre>

It almost works, but the tabs are being troublesome. It is trivial to replace the tabs with two spaces, but then non-whitespace characters are pushed over instead of absorbed into the tabs. True tabs absorb n-1 non-whitespace characters (where n is the number of spaces per tab).

For example, the following table should be displayed as so:

|   | 43| 43|  7|   |   |
| 12|128|128|128|   | 53|
|  3|  3|  3|  3|   |   |
|   |   | 21| 21| 39|   |

However by blindly replacing all tabs with two-spaces, we get this:

|    |  43|  43|    7|   |   |
|  12|128|128|128|   | 53|
|   3|   3|   3|   3|   |   |
|   |   |  21|  21|  39|   |

I’m trying to figure out a (reasonably easy) way to convert the tabs to spaces while accounting for tabs that don’t take up the full n spaces.

Answer 1

I have written this function some time ago, might be helpful:

function tab2space($line, $tab = 4, $nbsp = FALSE) {
    while (($t = mb_strpos($line,"\t")) !== FALSE) {
        $preTab = $t?mb_substr($line, 0, $t):'';
        $line = $preTab . str_repeat($nbsp?chr(7):' ', $tab-(mb_strlen($preTab)%$tab)) . mb_substr($line, $t+1);
    }
    return  $nbsp?str_replace($nbsp?chr(7):' ', ' ', $line):$line;
}

It was meant to deal with multibyte strings, if you have only numbers, you can get rid of mb_, it will speed up this function.

[+] Note that this is meant to work with one line, so you will need to process line by line with fgets instead of whole file at once.