$re = '/(("Data": ("){)(\\\\\".*){1,}(}("),))/m';
$str = '[so much data exists in the same single line ] ,"Comments": "New alert", "Data": "{\\"etype\\":\\"MalwareFamily\\",\\"at\\":\\"2024-06-21T11:34:07.0000000Z\\",\\"md\\":\\"2024-06-21T11:34:07.0000000Z\\",\\"Investigations\\":[{\\"$id\\":\\"1\\",\\"Id\\":\\"urn:ZappedUrlInvestigation:2cc87ae3\\",\\"InvestigationStatus\\":\\"Running\\"}],\\"InvestigationIds\\":[\\"urn:ZappedUrlInvestigation:2cc8782d063\\"],\\"Intent\\":\\"Probing\\",\\"ResourceIdentifiers\\":[{\\"$id\\":\\"2\\",\\"AadTenantId\\":\\"2dfb29-729c918\\",\\"Type\\":\\"AAD\\"}],\\"AzureResourceId\\":null,\\"WorkspaceId\\":null,\\"Metadata\\":{\\"CustomApps\\":null,\\"GenericInfo\\":null},\\"Entities\\":[{\\"$id\\":\\"3\\",\\"MailboxPrimaryAddress\\":\\"abc@gmail.com\\",\\"Upn\\":\\"abc@gmail.com\\",\\"AadId\\":\\"6eac3b76357\\",\\"RiskLevel\\":\\"None\\",\\"Type\\":\\"mailbox\\",\\"Urn\\":\\"urn:UserEntity:10338af2b6c\\",\\"Source\\":\\"TP\\",\\"FirstSeen\\":\\"0001-01-01T00:00:00\\"}, \\"StartTimeUtc\\": \\"2024-06-21T10:12:37\\", \\"Status\\": \\"Investigation Started\\"}", "EntityType": "MalwareFamily", [so much data exists in the same single line ]';
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