How to style a character in a string at specific index?

Question

Would you please give me some guidance on how to style one character in a string at specific index? the index of this string comes from an array and in some cases the array is empty, so I only need to style the character in the string if the array is not empty

$indices = array(74, 266); 

$string  = "CAGGACACTCTTTCTAGTGTTGATTCACCTCGAAGAAGGTCTGGCCTATTAAGAGATCAAGTTCAGTTGGTAAAAAGAAGCAACTCTGCTCGTTATGAGATAGTCCCGATTCAAGATCAACTATCATTTGAGAAGGGTTTCTTTATTGTAATCCGTGCATGCCAGTTGTTGGCTCAGAAGAATGAAGGCATTGTACTGGTGGGAGTCGCTGGTCCTTCAGGGGCCGGAAAGACCATGTTTACAGAAAAGATCCTGAATGTTATGCCTAGTATTGCAATCATAAACATGGACAACTACAATGATCCCAGTCGTATCATTGATGGAAACTTCGACG";

so how do I add a surround the character at the index 74 and 266 with a span so I can give it a different style?

my data is coming from the database so I need to make it dynamic.

Thanks

Answer 1

It's fairly easy: all you need is a few substrs in a loop and to keep track of the character count.

Here's a working code I made:

// zero-based indices
$indices = array(3, 10, 25);

// input
$in = 'abcDefghijKlmnopqrstuvwxyZ';

$openTag = '<b>';
$closeTag = '</b>';

$out = '';
$last = 0;
foreach($indices as $i) {
    $fragment = substr($in, $last, $i-$last);
    $letter = substr($in, $i, 1);
    $last = $i+1;

    $out .= $fragment . $openTag . $letter . $closeTag;
}

$out .= substr($in, $last);

// output
echo $out;

For this example, $out is abc<b>D</b>efghij<b>K</b>lmnopqrstuvwxy<b>Z</b>.

---

For convenience, here's it also as a function:

function highlightChars($text, $indices, $openTag, $closeTag) {
    $out = '';
    $last = 0;
    foreach($indices as $i) {
        $fragment = substr($text, $last, $i-$last);
        $letter = substr($text, $i, 1);
        $last = $i+1;

        $out .= $fragment . $openTag . $letter . $closeTag;
    }

    $out .= substr($text, $last);

    return $out;
}