Notes:
A regular expression is enclosed between two forward slashes “//“. Hash signs # or tildes ~ can also be used (these characters are called delimiters).
eg. $exp = “/php/“; – search for the occurence of string ‘php’
Special/meta-characters:
* Match zero or more of the preceding expression
+ Match one or more occurences of the preceding expression
? Match zero or one of the preceding expression
() brackets can be used to mark out sub patterns.