$re = '/\(\(\(?([^}]*?)\)\)\)/m';
$str = '((Short Title (in Navigation & Breadcrumb))) Pflanzen & Samen
((Post-Text)) Hast du unser Osterschoggi-Sortiment schon probiert? ((Schleckmaul))
[Ceci est un ((non visible)) (test)]
[[Ceci est un ((non visible)) (test)]]
Ceci est un [[visible ((non visible))]] (test)
Ceci est un ((non visible [non visible])) (test)
((Headline))
((non visible))
Ceci doit être traduit
((Sternchentext))
*Mit Cashback Fr. 39.90, Rückvergütung (Überweisung) einlösbar unter canon.ch/summer, gültig von 15.2. bis 15.5.2021 ((maximal 140 Zeichen inkl. Leerzeichen))
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';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php