- preg_quote: documentation ( source)
- preg_replace: documentation ( source)
<?php
$content = 'singleline';
$content = preg_quote($content);
$output = '<p>[@address|singleline]</p>';
$output = preg_replace('%(?<=@address|.)'.$content.'(?=[^\]\[]*\])%', "", $output);
echo $output;