Variables, Constants, and Expressions

Question 1

What is a valid variable name?

Answer 1

A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.

Question 2

What is a special variable that can’t be assigned?

Answer 2

$this

Question 3

What is a special variable that can’t be assigned?

Answer 3

$this

Question 4

What is the difference between assigning by value and assigning by reference?

Answer 4

By default, variables are always assigned by value; the entire value of the original expression is copied into the destination variable. After assigning one variable’s value to another, changing one of those variables will have no effect on the other.

When you assign by reference, the new variable points to the original variable. Changes to the new variable affect the original, and vice versa.

To assign by reference, simply prepend an ampersand to the beginning of the source variable.

Only named variables (and not unnamed expressions or functions) may be assigned by reference.

Question 5

Why are superglobals called superglobals?

Answer 5

Because they are automatically

Question 6

Why are superglobals called superglobals?

Answer 6

Because they are automatically available in every scope.

Question 7

Why are superglobals called superglobals?

Answer 7

Because they are automatically available in every scope.

Question 8

What is the scope of variables within a user-defined function?

Answer 8

The scope is limited to that function.

Question 9

Does the default scope span included and required files?

Answer 9

Yes.

Question 10

What do you need to do to use a global variable within a function?

Answer 10

Declare it as global within the function.

Question 11

What is a second way to access variables from the global scope?

Answer 11

Use the special PHP-defined $GLOBALS associative array. $GLOBALS is a superglobal.

Question 12

What is a static variable?

Answer 12

.

Question 13

What is a static variable?

Answer 13

A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope.

Question 14

What is a recursive function?

Answer 14

A function which calls itself.

Question 15

Can you assign values to a static variable if those values are the result of an expression.

Answer 15

No. This will result in a parse error.

Question 16

Are the static and global modifiers implemented in terms of value or reference?

Answer 16

Reference.

Question 17

What are the four different scope types for PHP variables/

Answer 17

Local, function, global, and static.

Question 18

What is a variable variable?

Answer 18

A variable name that can be set and used dynamically.

$a = 'hello';
\$\$a = 'world'; //Now there is a variable $hello with value 'world'

Question 19

What is the ambiguity problem when using variable variables with arrays?

Answer 19

If you write $$a[1], the parser doesn’t know if you meant to use $a[1] as a variable, or if you wanted $$a as the variable, and [1] as the index from that variable. So, for the first case, the syntax for resolving the ambiguity is ${$a[1]}, and for the second case, it’s ${$a}[1].

Question 20

When accessing class property names with variable variables, what is the scope?

Answer 20

The variable property name will be resolved within the scope from which the call is made.

Question 21

Where can variable variables NOT be used?

Answer 21

With PHP’s Superglobal arrays within functions or class methods. The variable $this also cannot be referenced dynamically.

Question 22

If a variable name in a GET or POST contains a period, what is it converted to?

Answer 22

An underscore.

Question 23

If an image is used as a form submit button, what additional data gets submitted with the form?

Answer 23

The variables sub_x and sub_y, which contain the coordinates of the user click within the image.

Question 24

If an image is used as a form submit button, what additional data gets submitted with the form?

Answer 24

The variables sub_x and sub_y, which contain the coordinates of the user click within the image.

Question 25

When can the setcookie() function be called?

Answer 25

Because cookies are part of the HTTP header, setcookie() must be called before any output is sent to the browser.

Question 26

How can you assign multiple values to a single cookie variable?

Answer 26

Assign it as an array:

setcookie(“MyCookie[foo]”, ‘Testing 1’, time()+3600);

This creates two separate cookies, although MyCookie will now be a single array in the script. To set just one cookie with multiple values, you can use serialize() or explode() on the value first.

Question 27

When will a cookie not replace a previous cookie by the same name?

Answer 27

When the path or domain is different.

Question 28

What is a bare string?

Answer 28

An unquoted string which does not match any known key or reserved words.

Question 29

What is a constant?

Answer 29

An identifier for a simple value that cannot change during execution of the script.

Question 30

How is a constant formatted?

Answer 30

A constant is case-sensitive by default, and always uppercase by convention. The name of a constant follows the same rules as any label in PHP. A valid constant name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.

Question 31

What is the scope of constants?

Answer 31

Global, just like superglobals.

Question 32

What is the scope of constants?

Answer 32

Global, just like superglobals.

Question 33

How is an expression defined?

Answer 33

“Anything that has a value”. Almost anything you write in PHP is an expression.

Question 34

What is a scalar value?

Answer 34

A value that you can’t break down into smaller pieces, unlike an array.

Question 35

Which scalar and non-scalar (composite) values does PHP support?

Answer 35

scalar: integer, float, string, boolean
composite: array, object

Question 36

What is the ternary conditional operator?

Answer 36

$first ? $second : $third

If $first is true, then $second is evaluated. If not, then $third is evaluated.

Question 37

What is the ternary conditional operator?

Answer 37

$first ? $second : $third

If $first is true, then $second is evaluated. If not, then $third is evaluated.

Question 38

$a = 1;
$b = $a++;

What does $b equal? What does $a equal?

Answer 38

Now, $b equals 1, and $a equals 2.

$a is assigned to $b BEFORE $a is incremented.