<?php
$line="This is the first test.{@font-face:Garamond}";
$line=preg_replace_callback("/(?<![\]\\])\{([\w\s\\@:=\'\"-\.;^}]*)(?<!\\)\}/",function ($match){print_r($match);return 'foo';},$line);
echo $line;
Warning: preg_replace_callback(): Compilation failed: missing closing parenthesis at offset 42 in /in/hSN6c on line 3
Output for 8.3.5
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
Warning: preg_replace_callback(): Compilation failed: missing closing parenthesis at offset 42 in /in/hSN6c on line 3