What does a special set of tags <?= and ?> do in PHP?

Its called short tag , in this case the output is directly displayed on the browser without using the echo or print statement.

What’s the difference between include and require,include_once and require_once? – In case of include and require it differ in how they handle failures. If the file is not found by require(), it will definatly cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.

Where as in case of include_once and require_once the basic differnence remain the same as the above mentioned but both have a common feature in which the script or the file is included only once irrespective of how many times a file is included in the program , it definatley fast up the execution where same file is included many times.

PHP Interpreter treats numbers beginning with 0 as octal. Thats the main reason.

Would I use print “$a dollars” or “{$a} dollars” to print out the amount of dollars in this example? – In this example it wouldn’t matter, since the variable is all by itself, but if you were to print something like “{$a},000,000 mln dollars”, then you definitely need to use the braces.

How do you define a constant? -

We can do this by define() directive, like define("ROOT", "localhost"); and A valid constant name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.

How do you pass a variable by value? -

As we do in C++, place an ampersand in front of it, like $a = &$b

Will comparison of string “10″ and integer 11 work in PHP? -

Yes, internally PHP will cast everything to the integer type, so numbers 10 and 11 will be compared.

When are you supposed to use endif to end the conditional statement?

When the original if was followed by : and then the code block without braces.