iOS provides the Erase All Content and Settings option to wipe the data on an iPhone. This type of data wipe erases user settings and information by removing the encryption keys that protect the data. As the encryption keys are erased from the device, it is not possible to recover the deleted data, not even during forensic investigations. Other wiping methods are available that overwrite the data in the device memory. More information on wiping can be found at https://support.apple.com/en-in/HT201274.