Control Structures

Question 1

What is a statement-group?

Answer 1

A group of statements encapsulated with curly braces, that itself is also a statement.

Question 2

When can using ‘else if’ instead of ‘elsif’ be problematic?

Answer 2

When using a colon to define your if/elseif conditions. It will fail with a parse error.

Question 3

What is the alternative syntax for control structures?

Answer 3

For if, while, for, foreach, and switch, the basic form of the alternate syntax is to change the opening brace to a colon (:) and the closing brace to endif;, endwhile;, endfor;, endforeach;, or endswitch;, respectively.

Question 4

Any output (including whitespace) between a switch statement and the first case…

Answer 4

…will result in a syntax error.

Question 5

Any output (including whitespace) between a switch statement and the first case…

Answer 5

…will result in a syntax error.

Question 6

Any output (including whitespace) between a switch statement and the first case…

Answer 6

…will result in a syntax error.

Question 7

What happens when an expression in a for loop is empty?

Answer 7

It’s skipped. expr2 being empty means the loop should be run indefinitely.

Question 8

What happens when multiple expressions separated by commas are in a for loop?

Answer 8

In expr2, all expressions separated by a comma are evaluated but the result is taken from the last part.

Question 9

What happens when multiple expressions separated by commas are in a for loop?

Answer 9

In expr2, all expressions separated by a comma are evaluated but the result is taken from the last part.

Question 10

What does foreach work on?

Answer 10

Only on arrays and objects. When you try to use it on a variable with a different data type, or on an unitialized variable, it will issue an error.

Question 11

Why don’t you need to call reset() before a foreach loop?

Answer 11

When foreach first starts executing, the internal array pointer is automatically reset to the first element of the array.

Question 12

How can you directly modify array elements within a foreach loop?

Answer 12

Precede $value with &, and the value will be assigned by reference. Like this:

Question 13

How can you directly modify array elements within a foreach loop?

Answer 13

Precede $value with &, and the value will be assigned by reference. Like this:

Question 14

Is ‘break 0’ or ‘continue 0’ valid now?

Answer 14

No.

Question 15

Can you pass in variables to break or continue: break $num?

Answer 15

No.

Question 16

When can a break statement end the entire script?

Answer 16

When it’s not in a control loop.

Question 17

What does continue do?

Answer 17

It’s used within looping structures to skip the rest of the current loop iteration and continue execution at the condition evaluation and then the beginning of the next iteration.

Question 18

What is the default value for continue or break?

Answer 18

1

Question 19

What is the default value for continue or break?

Answer 19

1

Question 20

In a switch statement, what are the limits on the case expression?

Answer 20

It can be any expression that evaluates to an integer or floating-point number or string.

Question 21

What are the directives you can set using declare?

Answer 21

Ticks and encoding.

Question 22

What can be given as directive values using declare?

Answer 22

Only literals, not variables or constants.

Question 23

What is a tick?

Answer 23

e

Question 24

What is a tick?

Answer 24

An event that occurs for every N low-level tickable statements executed by the parser within the declare block. The value for N is specified using ticks=N within the declare block’s directive section.

Question 25

How do you specify an event to occur on each tick?

Answer 25

Use register_tick_function().

Question 26

What does return do?

Answer 26

It's a language construct that returns program control to the calling module. Execution resumes at the statement following the called module's invocation.

Question 27

What happens if return is called from within a function?

Answer 27

It immediately ends execution of the current function, and returns its argument as the value of the function call. return also ends the execution of an eval() statement or script file.

Question 28

What happens if return is called from the global scope?

Answer 28

If called from the global scope, then execution of the current script file is ended. If the current script file was included or required, then control is passed back to the calling file. Furthermore, if the current script file was included, then the value given to return will be returned as the value of the include call. If return is called from within the main script file, then script execution ends. If the current script file was named by the auto_prepend_file or auto_append_file configuration options in php.ini, then that script file's execution is ended.

Question 29

What is the difference between require and include?

Answer 29

Upon failure, require produces a fatal error AND a warning, whereas include produces only a warning. Otherwise they are identical.

Question 30

Where does include() check for files?

Answer 30

If the file isn't found in the include_path, include will finally check in the calling script's own directory and the current working directory before failing.

Question 31

What is the scope of an included file?

Answer 31

When a file is included, the code it contains inherits the variable scope of the line on which the include occurs. Any variables available at that line in the calling file will be available within the called file, from that point forward. However, all functions and classes defined in the included file have the global scope.

Question 32

What is the scope of an included file?

Answer 32

When a file is included, the code it contains inherits the variable scope of the line on which the include occurs. Any variables available at that line in the calling file will be available within the called file, from that point forward. However, all functions and classes defined in the included file have the global scope.

Question 33

What happens when a file is included from inside of a function?

Answer 33

If the include occurs inside a function within the calling file, then all of the code contained in the called file will behave as though it had been defined inside that function. So, it will follow the variable scope of that function. An exception to this rule are magic constants which are evaluated by the parser before the include occurs.

Question 34

How is PHP parsing handled in included files?

Answer 34

When a file is included, parsing drops out of PHP mode and into HTML mode at the beginning of the target file, and resumes again at the end. For this reason, any code inside the target file which should be executed as PHP code must be enclosed within valid PHP start and end tags.

Question 35

What are URL include wrappers?

Answer 35

A means for allowing files to be included using a URL instead of a local pathname. If the target server interprets the target file as PHP code, variables may be passed to the included file using a URL request string as used with HTTP GET.

Question 36

What does include return?

Answer 36

Include returns FALSE on failure and raises a warning. Successful includes, unless overridden by the included file, return 1

Question 37

Can you execute a return statement inside an included file in order to terminate processing in that file and return to the script which called it?

Answer 37

Yes. Also, it's possible to return values from included files.

Question 38

Do you need parentheses around the argument to include?

Answer 38

No, because it is a special language construct.

Question 39

What is the goto operator used for?

Answer 39

The goto operator can be used to jump to another section in the program. The target point is specified by a label followed by a colon, and the instruction is given as goto followed by the desired target label. This is not a full unrestricted goto. The target label must be within the same file and context, meaning that you cannot jump out of a function or method, nor can you jump into one. You also cannot jump into any sort of loop or switch structure. You may jump out of these, and a common use is to use a goto in place of a multi-level break.