PHP has seven data types. The seven types are:
Strings hold characters such as "a," "abc," "www.java2s.com," etc. PHP strings are case-sensitive.
Objects are complex variables that have multiple values, and they can have their own functions.
Resources might be picture data, or the result of an SQL query. We should free up resources after using them.
Reference type variables are actually pointer to the real data. Once two variables are pointing to the same data, you can change either variable and the other one will also update.
When you use the = (assignment) operator, PHP takes the value from operand two and copies it into operand one.
To assign by reference, you need to use the reference operator
&) after the equals operator (=),
<?PHP//from w w w .ja va 2 s. com $a = 10; $b =& $a; print $a; print $b; ++$a; print $a; print "\n"; print $b; print "\n"; ++$b; print $a; print "\n"; print $b; print "\n"; ?>
The code above generates the following result.
As of PHP 5, objects are passed and assigned by reference by default. Assigning an object variable is actually copying its object handle, which means the copy will reference the same object as the original.
References allow a function to work directly on a variable rather than on a copy.