<?php
$link = 'https://d...content-available-to-author-only...1.ru/imgs/123';
$result = [
'https://d...content-available-to-author-only...1.ru/imgs/123',
'https://d...content-available-to-author-only...1.ru/imgs/1230',
'https://d...content-available-to-author-only...1.ru/imgs/1231',
'https://d...content-available-to-author-only...1.ru/imgs/1232',
];
$result = preg_replace("~^($link)(?=.)(.*)$~", "$1<b>$2</b>", $result);
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