$re = '/(?<=displayImportingConfirmationMessage\(\').*(?<=})/';
$str = '<script>parent.displayImportingConfirmationMessage(\'{"temporaryZipFile":"/opt/fluig/volume/upload/adm/pageImport/pageUpload2572076996793369742WCMPageExport.zip","expandedDirectoryZipFile":"/opt/fluig/volume/upload/adm/pageImport/expandedPage_3205464082306670499","itemName":"WCMPageExport.zip","isItemFormField":false,"pages":[{"title":"Home","description":"Home","pageKey":{"code":"home"},"displayOrder":10,"childrens":[],"enabledChildren":false,"enabledPathParam":false,"enabledMobileApp":false,"editable":true,"disableChildLevel":false,"menuGroup":false,"iconUploaded":false,"hidden":false,"enabled":true,"opened":false,"depthLevel":-1,"preferences":{}}]}\');</script>
';
preg_match_all($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