これは非常に詳細なコードです...もっと短くすることができます...
<?php
$longtext = "my long text string (with another string)";
$firstParantheses = strpos($longtext,"(");
$firstText = substr($longtext,0,$firstParantheses);
$secondText = substr($longtext,$firstParantheses);
$secondTextWithoutParantheses = str_replace("(","",$secondText);
$secondTextWithoutParantheses = str_replace(")","",$secondTextWithoutParantheses);
$finalFirstPart = $firstText;
$finalSecondPart = $secondTextWithoutParantheses;
echo $finalFirstPart." ------- ".$finalSecondPart;
?>