[PHP] significance of escape character in string in PHP

[Norah Jones]

I am having an string which was have few ' (single quote) and few " (double 
quotes) and was not able to insert into the mysql database. I have replaced 
them with \' and \" and everything is fine.
Though this are fine now but don't understand the working and I could have 
missed few corner cases also. Please suggest the working and also if there is 
some better way to achieve this.