asked on

PHP: Undefined offset with usort and preg_match

This does not work if the array contains special characters:

<pre><?php

$arr = Array ( 'xa0.txt', 'xa1.txt', 'xa10.txt', 'xa11.txt', 'xa12.txt', 'xa2.txt', 'xa3.txt', 'xa4.txt', 'xa5.txt', 'xa6.txt', 'xa7.txt', 'xa8.txt', 'xa9.txt');
usort($arr, 'cmp');
print_r($arr);

$arr = Array ( 'a/b/c_d-e555/xa0.txt', 'a/b/c_d-e555/xa1.txt', 'a/b/c_d-e555/xa10.txt',  'a/b/c_d-e555/xb10.txt', 'a/b/c_d-e555/xb11.txt', 'a/b/c_d-e555/xb2.txt', 'a/b/c_d-e555/xb1.txt', 'a/b/c_d-e555/xa11.txt', 'a/b/c_d-e555/xa12.txt', 'a/b/c_d-e555/xa2.txt', 'a/b/c_d-e555/xa3.txt', 'a/b/c_d-e555/xa4.txt', 'a/b/c_d-e555/xa5.txt', 'a/b/c_d-e555/xa6.txt', 'a/b/c_d-e555/xa7.txt', 'a/b/c_d-e555/xa8.txt', 'a/b/c_d-e555/xa9.txt');
usort($arr, 'cmp');
print_r($arr);

function cmp($a, $b) {
    $a = zeroadd($a);
    $b = zeroadd($b);
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

function zeroadd($a) {
    preg_match('/^(\w+)(\d+)(\.\w+)$/', $a, $bits);
    return sprintf("%s%05d%s",$bits[1],$bits[2],$bits[3]);
}

?></pre>

Open in new window

Lee Wadwell

What do you want to sort on?
- the entire path and file name with name adjusted to have leading zeroes; or
- just the file name adjusted to have leading zeroes

If everything + the filename etc try the preg_match() in the zeroadd function
preg_match('/^(.+)(\d+)(\.\w+)$/', $a, $bits);

But to depending on what you could throw at it ... the regex may need further refinement.

Lee Wadwell

A slightly safer approach would to handle non-matching strings ... e.g.

function zeroadd($a) {
    if ( preg_match('/^(.+)(\d+)(\.\w+)$/', $a, $bits) )
        return sprintf("%s%05d%s",$bits[1],$bits[2],$bits[3]);
    else
        return $a;
}

Open in new window

Ray Paseur

Please answer the question asked here:
https://www.experts-exchange.com/questions/27848911/PHP-Sort-Array-Ascending-With-or-Without-Trailing-Zeros.html?anchorAnswerId=38353128#a38353128

What we're trying to get is a dialog that will lead us to an acceptably clear description of the input data and the outputs you want. Computer programming only does one thing: It transforms one data set into another data set. If we have fragments of the truth about the data, we are unlikely to give you anything more than fragments of an answer.

Ray Paseur

The output from this seems intuitively correct, but it would be better to know for sure that we had a representative test data set.

<?php // RAY_temp_hankknight.php
error_reporting(E_ALL);
echo '<pre>';

$arr = array
( 'xa0.txt'
, 'xa1.txt'
, 'xa10.txt'
, 'xa11.txt'
, 'xa12.txt'
, 'xa2.txt'
, 'xa3.txt'
, 'xa4.txt'
, 'xa5.txt'
, 'xa6.txt'
, 'xa7.txt'
, 'xa8.txt'
, 'xa9.txt'
)
;
natsort($arr);
print_r($arr);

$arr = array
( 'a/b/c_d-e555/xa0.txt'
, 'a/b/c_d-e555/xa1.txt'
, 'a/b/c_d-e555/xa10.txt'
, 'a/b/c_d-e555/xb10.txt'
, 'a/b/c_d-e555/xb11.txt'
, 'a/b/c_d-e555/xb2.txt'
, 'a/b/c_d-e555/xb1.txt'
, 'a/b/c_d-e555/xa11.txt'
, 'a/b/c_d-e555/xa12.txt'
, 'a/b/c_d-e555/xa2.txt'
, 'a/b/c_d-e555/xa3.txt'
, 'a/b/c_d-e555/xa4.txt'
, 'a/b/c_d-e555/xa5.txt'
, 'a/b/c_d-e555/xa6.txt'
, 'a/b/c_d-e555/xa7.txt'
, 'a/b/c_d-e555/xa8.txt'
, 'a/b/c_d-e555/xa9.txt'
)
;
natsort($arr);
print_r($arr);

Open in new window

HTH, ~Ray

ASKER CERTIFIED SOLUTION

Ray Paseur

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hankknight

ASKER

natsort() does exactly what I need!