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Learning PHP, MySQL, and JavaScript by Robin Nixon

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Chapter 3 Answers

Question 3-1

The tag used to start PHP interpreting code is <?php ... ?>, which can be shortened to <? ... ?>.

Question 3-2

You can use // for a single line comment or /* ... */ to span multiple lines.

Question 3-3

All PHP statements must end with a semicolon (;).

Question 3-4

With the exception of constants, all PHP variables must begin with $.

Question 3-5

Variables hold a value that can be a string, a number, or other data.

Question 3-6

$variable = 1 is an assignment statement, whereas $variable == 1 is a comparison operator. Use $variable = 1 to set the value of $variable. Use $variable == 1 to find out later in the program whether $variable equals 1. If you mistakenly use $variable = 1 where you meant to do a comparison, it will do two things you probably don’t want: set $variable to 1 and return a true value all the time, no matter what its previous value was.

Question 3-7

A hyphen is reserved for the subtraction operators. A construct like $current-user would be harder to interpret if hyphens were also allowed in variable names and, in any case, would lead programs to be ambiguous.

Question 3-8

Variable names are case-sensitive. $This_Variable is not the same as $this_variable.

Question 3-9

You cannot use spaces in variable names, as this would confuse the PHP parser. Instead try using the _ (underscore).

Question 3-10

To convert one variable type to another, reference it and PHP will automatically convert it for you.

Question 3-11

There is no difference between ++$j and $j++ ...

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