PHP - Check for duplicate in an array and update the duplicate value in loop

Question

$mymarker = '/MARKER[0-9]{2}/';
preg_match_all($mymarker, $mycontent, $matches);
var_dump($matches);

Gives:

array(1) {
  [0]=>
  array(18) {
    [0]=>
    string(8) "MARKER00"
    [1]=>
    string(8) "MARKER01"
    [2]=>
    string(8) "MARKER02"
    [3]=>
    string(8) "MARKER04"
    [4]=>
    string(8) "MARKER05"
    [5]=>
    string(8) "MARKER07"
    [6]=>
    string(8) "MARKER09"
    [7]=>
    string(8) "MARKER13"
    [8]=>
    string(8) "MARKER13"
    [9]=>
    string(8) "MARKER16"
    [10]=>
    string(8) "MARKER15"
    [11]=>
    string(8) "MARKER21"
    [12]=>
    string(8) "MARKER31"
    [13]=>
    string(8) "MARKER22"
    [14]=>
    string(8) "MARKER24"
    [15]=>
    string(8) "MARKER26"
    [16]=>
    string(8) "MARKER80"
    [17]=>
    string(8) "MARKER81"
  }
}

As we see, MARKER13 occurs twice. This duplicate instance can occur with MARKER05, MARKER07 and MARKER13.

The second value is needed to be updated to MARKERXX+1 so Second occurrence of:

Marker05 will have to be updated to MARKER06 Marker07 will have to be updated to MARKER08 MARKER13 will have to be updated to MARKER14.

How can we set this up in a loop, to check for dups and update the duplicate value to the next value.

Thanks

Jan · Accepted Answer · 2016-02-22 20:58:01Z

2

There might be easier ways, but you could come up with the following

<?php
$matches = array("MARKER00","MARKER01","MARKER02","MARKER04","MARKER05","MARKER07","MARKER09","MARKER13","MARKER13","MARKER16","MARKER15","MARKER21","MARKER31","MARKER22","MARKER24","MARKER26","MARKER80","MARKER81");

$duplicates = array("MARKER05", "MARKER07", "MARKER13");
$len = count($matches);

for ($i=0;$i<$len;$i++) {
    $marker = $matches[$i];

    if (in_array($marker, $duplicates)) {
        // one of our markers
        // check if the next is the same
        // if so update it
        if ($i<$len-1) {
            if ($marker == $matches[$i+1]) {
                # split the string into a letter and a digit part
                # with lookarounds (behind/ahead, both positive)
                list($text,$number) = preg_split('~(?<=[A-Z])(?=\d)~', $matches[$i+1]);
                $number = intval($number);
                # increase the intval'd number by one
                # and apply it to the original array
                $number += 1;
                $matches[$i+1] = $text . $number;
            }
        }
    }
}

print_r($matches);
// updated to MARKER14

?>

Apparently, this works only if the array is ordered, ie duplicates follow up.

edited Feb 22, 2016 at 20:58

answered Feb 21, 2016 at 9:00

Jan

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1 Comment

rusticnomad Over a year ago

Thanks. Your reply gave me an idea of avoiding the loop part. MARKERXX are positions in html document that I am splitting on MARKERXX and next MARKERXX in sequence (XX can be any number and not necessarily ordered) to map to db column. MARKERXX are obtained thru preg_replace. So, since only fixed (3) numbers of markers could repeat across the entire files set, I ran the preg_replace($patterns, $replacements, 1) twice once with 05, 07, 13 and next time with 06, 08 and 14 and got non repeating MARKERSXX in the array. :)

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