Aidan Lister

When outputting code in a browser, or automatically formatting someone else’s code, it’s handy to be able to accurately convert tabs to spaces.

This function converts tabs to the appropriate number of spaces to preserve formatting.

/**
 * Converts tabs to the appropriate amount of spaces while preserving formatting
 *
 * @author      Aidan Lister <aidan@php.net>
 * @version     1.2.0
 * @link        http://aidanlister.com/2004/04/handling-tab-to-space-conversions/
 * @param       string    $text     The text to convert
 * @param       int       $spaces   Number of spaces per tab column
 * @return      string    The text with tabs replaced
 */
function tab2space ($text, $spaces = 4)
{
    // Explode the text into an array of single lines
    $lines = explode("\n", $text);

    // Loop through each line
    foreach ($lines as $line) {

        // Break out of the loop when there are no more tabs to replace
        while (false !== $tab_pos = strpos($line, "\t")) {

            // Break the string apart, insert spaces then concatenate
            $start = substr($line, 0, $tab_pos);
            $tab   = str_repeat(' ', $spaces - $tab_pos % $spaces);
            $end   = substr($line, $tab_pos + 1);
            $line  = $start . $tab . $end;
        }

        $result[] = $line;
    }

    return implode("\n", $result);
}

A quick example:

$data  = "fooo\t\tbar\n";
$data .= "foooo\t\tbar\n";
$data .= "fooooo\t\tbar\n";

echo "This is the example data:\n";
echo $data;
echo "n";

echo "With simple replace:\n";
echo str_replace("\t", "    ", $data);
echo "n";

echo "With tab2space:\n";
echo tab2space($data, 8);

This would produce the following output:

This is the example data:
fooo		bar
foooo		bar
fooooo		bar

With simple replace:
fooo        bar
foooo        bar
fooooo        bar

With tab2space:
fooo            bar
foooo           bar
fooooo          bar