Zend Php 5 Certificaiton - Php Basics

Front 1

What languages influence PHP syntax

Back 1

Prdominantly C language, but influence from PERL. Recent object-orenented syntax from JAVA

Front 2

What are the four types of PHP tags?

Back 2

Standard <?php code ?>
Short <? code ?> & <?= $variable ?>
Script <script language="php"> code </script>
ASP <% code %>

Front 3

What PHP tags should be used and why?

Back 3

Standard <?php code ?>

Best solution for portablility and backwards compatiblity. Also, cannot be disabled in PHP config file.

Other tags are considered depreciated.

Front 4

What character is used to terminate PHP statements?

Back 4

;

This is not required for the last statement in the closing tag, but should be added for consistency.

Front 5

How is a line commented? Multi-line commented?

Back 5

Single line: // line
# line
Multi-line: /* line1
line2
*/

Front 6

Where are three places where you CANNOT use whitespace characters?

Back 6

- Between <? and php
- To break apart keywords (e.g whi le, funct ion>
)
- To break apart variable and function names (e.g. $var name, function foo bar)

Front 7

What characters define a code block?

Back 7

"{" and "}"

Front 8

What is a language construct?

Back 8

Elements pre-built into the language that follow special rules. The most common in PHP is the echo construct. It is not a function since is does not return a value.

Front 9

What are the two general categories of PHP data types and their differences?

Back 9

Scalar: Contain one value at a time
Composite: Containers of other data

Front 10

What are the four scalar data types?

Back 10

Boolean: Either true or false
int: signed numeric iteger value
float: signed floating-point value
string: collection of binary data

Front 11

What are the three different notation of integers PHP supports?

Back 11

Decimal: 10; -11; 1452: No thousand separator needed, or allowed
Octal: 0666; 0100: Identified by leading zero, used mainly to identify UNIX permisions
Hexadecmial: 0x123; 0XFF; -0x100: Base 16 notation, leading 0x that is case insensitive

Front 12

What are the two different notations of floating-point numbers PHP supports?

Back 12

Decimal: 0.12, 12.14, -.123: Traditional decimal notation
Exponential: 2E7, 1.2e2: a set of significant digits (also called mantissa), followed by the case-insensitive letter E and then by an exponent. The resulting number is expressed multiplied by 10 to the power of the exponent, for example, 1e2 equals 100.

Front 13

Can the precision and range of numbers vary in PHP, and if so, why?

Back 13

Yes. Depending on how PHP was complied, on a 64 bit platform, maybe capable of wider range then on 32 bit platform.

Front 14

Does PHP track overflows?

Back 14

No.

Front 15

Consider the following statement:

echo (int) ((0.1 + 0.7) * 10)
What is printed out and why?

Back 15

7. This is because prior to the int conversion, the number is stored as 7.999999 instead of 8. The int conversion chops the remander off. Because of this, you should consider using the BCMath exension instead of PHP built in data types

Front 16

Many programmers consider strings equivilant to text. Is this the case in PHP? Why or why not?

Back 16

This is not the case in PHP. Strings are considered binary data. Due to this, you could store text, image files, spreadsheet, music recordings, etc in string data types.

Front 17

Describe data-type conversions for the following:
Number converted to a Boolean
String converted to a Boolean
Boolean converted to a number or string

Back 17

A number to a boolean becomes false if the original value is zero, true otherwise
A string converted to a boolean is false if it is empty or equals "0". If it contains other data, even multiple zeros, it is true.
When boolean is converted to a number or string, 1 if true, 0 if false

Front 18

What two compound data types are supported in PHP?

Back 18

Array: Containers of ordered data elements that can contain other data types, event other arrays
Objects: Containers of both data and code. Form basis of Object Oriented programing

Front 19

What two other data types, aside from Scaler and Compound are found in PHP?

Back 19

NULL: indicates a variable has no value.
resource: used to indicate external resources that are not natively used by PHP, such as a file handle.

Front 20

What is type conversion and how does a user force it in PHP?

Back 20

Type conversion is converting from one data type to another. This is done by placing the type you want to convert to in brackets before the expression. Example:
$x = 10.88;
echo (int) $x; //outputs 10

Not that you cannot convert any value to a resource, but you can convert a resource to a value, resulting in the resource's ID number.

Front 21

PHP variables are "loosely typed" while other languages are "strongly typed." What is the difference between the two?

Back 21

Loosely typed: implicitly change the type of the variable as needed depending on the operation being performed on it's value

Strongly typed: variable can only contain one type of data throughout its existence.

Front 22

What are the rules for naming variable in PHP?

Back 22

Number, letters and underscore only allowed. Variable must start with underscore or letter.

Front 23

What is a variable variable?

Back 23

It is the process of taking the value of one variable and using it has the name of another variable using the "$$" syntax. Example:
$name = 'foo';
$$name = 'bar';
echo $foo; //Displays 'bar'

Due to this, it is possible to create variable names that do not follow PHP variable naming rules. Use extreme care since they can make code difficult to understand and improper use could lead to security issues.

Front 24

Describe what the following code will do in PHP:

function myFunc() {
echo 'myFunc!';
}

$f = 'myFunc';
$f();

Back 24

Setting $f to 'myFunc' and then executing the statement $f() will execute the function called 'myFunc', echoing out "myFunc!"

Front 25

What does the function isset() do in PHP?

Example:
echo isset ($x);

Back 25

Will return true if variable exists AND has a value other then NULL.

Front 26

How do you define a constant in PHP?

Back 26

Use the 'define' function:

define('EMAIL', '[e-mail]');
echo EMAIL; //Display [e-mail]

Front 27

What are the naming rules for constants in PHP?

Back 27

They can contain only letters, numbers and underscores. They should be named in uppercase letters as in standard programing practices, but is not required.

Front 28

What are the various operators used in PHP?

Back 28

Assignment: assign data to variables
Arithmetic: perform basic math functions
String: join two or more strings
Comparision: compare two pieces of data
Logical: perform logical operations on boolean data

Bitwise: manipulating bits using boolean math
Error Control: suppressing errors
Execution: executing system commands
Incrementing/Decrementing: incrementing and decrementing numberical values
Type: identifying objects

Front 29

What are the five arithmetic operators used in PHP?

Back 29

Addition: $a = 1 +3.5;
Subtraction: $a = 4 - 2;
Multiplication: $a = 8 * 3:
Division: $a = 15 / 5;
Modulus: $a = 23 % 7;

Front 30

How are incrementing and decrementing operators used in PHP? What are their symbols?

Back 30

If the operator is placed after its operand, the interpreter will first return the value of the latter (unchanged), then then increment/decrement it by 1


If the operator is placed before the operand, the interpeter will first increment/decrement the value of the latter, and then return the newly calculated value.
Example:
$a = 1;
echo $a++ //Output 1, $a now equal to 2
echo ++$a; //Output 3, $a now equal to 3
echo --$a: //Output 2, $a now equal to 2
echo $a-- //Output 2, $a now equal to 1

Front 31

How are strings concatenated in PHP?

Back 31

Using the "." character.

Example: $var1 . $var2

Front 32

What data type will bitwise operators only work on? What if they aren't that data type?

Back 32

Integers. If the operands are not integers, the interpreter will attempt to convert them.

Front 33

What are the six bitwise operators and how they are represented?

Back 33

Not: ~
AND: &
OR: |
XOR: ^
Left Shift: <<
Right Shift: >>

Front 34

How to the bitwise operators shift right/left work?

Back 34

Shift Left: shifts bits left resulting in multiplication.
$x = 1;
echo $x << 1 // Outputs 2
echo $x << 2 // Outputs 4

Shift Right: shifts bits right resulting in division.
$x = 8;
echo $x >> 1 // Outputs 4
echo $x >> 2 // Outputs 2

Front 35

Why must you be carefull when using the bitwise operators right/left shift?

Back 35

It is possible to shift the bits out of the integer type that holds them, resulting in either overflow or underflow scenarios.

Front 36

By default, assignment operators work by value. What does this mean?

Back 36

When you assign a variable to another, its value is copied to the variable. Any change made to the copied value does not affect the original variable.

Front 37

Describe how to assign variable by reference and what that means.

Back 37

To pass a variable by reference, you use the "&" character.
Example:
$a = 10;
$b = &$a; //by reference
$b = 20;
echo $a; //Outputs 20

This works for all data types, except objects, which are always passed by reference.

Front 38

In comparision operators, what are the four equivalence operations?

Back 38

== Equivalence, true if both operands can be converted to a common datatype and are equal
=== Identity, true if only the datatypes are the same and the values are the same.
!= Not Equivalent, true if both operands are not equivalent, with out regards to data type
!== Not Identical, true if both operands are not of the same data type or do not have the same value

Front 39

What comparision operators are used for greater/less then?

Back 39

< and <=, less then; less then or equal to

> and >=, greater then, or greater then or equal to

Front 40

What are the four logical operators used in PHP and their symbols?

Back 40

NOT: "!" prior to operand: !$a
AND: "&&" or "and": $a and $b, $a && $b
OR: "||" or "or": $a || $b, $a or $b
Exclusive OR: "XOR": $a XOR $b

Front 41

Out of the four logical operators, why is the NOT operator different?

Back 41

The NOT "!" operator is urinary and works on one operand, while the other three are binary and work on two operands.

Front 42

If the left-hand operand evaluates to false in an AND operation, is the right-hand side evaluated?

Back 42

Not in PHP, if the left-hand side is false, the right-hand side is never evaluated.

Front 43

What is the error suppression operator?

Back 43

The "@" symbol is used for the error suppression operator. If it it prepends an expression, then it will prevent PHP from outputting an error, provided that the function uses PHP's own functionality to report errors.

Example:

$x = @mysql_connect();

Front 44

How would you execute shell commands in PHP?

Back 44

You can use the backtick operator to execute shell commands.

Example:

$a = `ls -l`;

Front 45

What is operator associativity?

Back 45

Associativity is the direction operations are performed on an operation. This can be left to right, right to left, or none.

Front 46

What is a control structure?

Back 46

They allow you to control the flow of a script. Examples of these are if statements, loops, etc.

Front 47

What are conditional structures and examples there of?

Back 47

Conditional structures are used to change the flow of a script based on one or more conditions.

Example:

if (expression){
}
elseif (expression){
}
else (expression){
}

10 == $x ? 'YES' : 'NO";

switch($a){
case true:
break;
default;
break
}

Front 48

What ternary operator is used as a shortcut for if-then-else?

Back 48

Example:

echo 10 == $x ? 'YES' : 'NO";

Same as:

if (10 == $x){
echo 'YES';
}
else{
echo 'NO';
}

Front 49

Describe a switch construct?

Back 49

An initial expression is evaluated once, then compared to individual case values. A break statement is required to break out of the statement, or cases below the match will continue to be executed.

Example:

$a = true;
switch($a){
case true:
echo "true";
break;
default;
echo "not true";
break
}

Front 50

What is an iterative construct?

Back 50

Iterative constructs make it possible to run the same portion of code multiple times. These are more commonly known as loops.

Front 51

How many iterative constructs does PHP have and what are they?

Back 51

Four, although only two are necessary to the functioning of the language.

while (condition){//code}
do{code}while(condition);
for(start instruction, condition, end loop instruction){//code};
foreach(array as value){//code}

Front 52

How does the break keyword affect a loop?

Back 52

When the break keywords is encountered in a loop, the loop will be exited at that point.

Front 53

In the following code snippet, what does "break 2" mean:

for ($i = 0; $i < 10; $i++){
for ($j = 0; $j < 3; $j++){
if (($j+ $i) % 5 == 0){
break 2;
}
}
}

Back 53

Adding a number after the break keyword tells the interpreter how many nested loops to break out of. In this example, "break 2" will break out of both loops.

Front 54

Why should you always remember to end the "break" statement with a semi-colon?

Back 54

If the break statement does not end with a semi-colon, and the code right after returns an integer, then this is appended to the break statement, possibly breaking out of multiple loops when not intended to.

Example;

$a = 1;
break
$a + 1;

would equivalate to break 2;

Front 55

What does the "continue" keyword do in a loop?

Back 55

The continue keyword will stop the rest of the code from executing in the loop, and start a new iteration of the loop.

Example:

while(true){
echo "hello";
continue;
echo "there";
}

"hello" will be echoed forever, but "there" will never be echoed.

Front 56

What are the five error levels in PHP?

Back 56

Compile-time errors: Errors detected by the parser while it is compiling a script. Cannot be trapped in the script itself.

Fatal errors: Errors that halt the execution of a script. Cannot be trapped.

Recoverable errors: Errors that represent significant failures, but can still be handled in a safe way.

Warnings: Recoverable errors that indicate a run-time fault. Do not halt the execution of a script.

Notices: Indicate that an error condition occurred, but is not necessarily significant. Do not halt the execution of a script.

Front 57

By default, PHP reports errors it encounters to the scripts output. Why is this bad in a production environment and how can it be turned off?

Back 57

Displaying all errors to users in a production environment is bad form, and a possible security issue. To disable errors from being displayed, in the php.ini add/edit the following line to the following:

display_errors = Off

Front 58

What function can be used to set your own error handler in PHP?

Back 58

set_error_handler(error_function,error_types)

<?php
//error handler function
function customError($errno, $errstr, $errfile, $errline)
{
echo "<b>Custom error:</b> [$errno] $errstr<br />";
echo " Error on line $errline in $errfile<br />";
echo "Ending Script";
die();
}

//set error handler
set_error_handler("customError");

$test=2;

//trigger error
if ($test>1)
{
trigger_error("A custom error has been triggered");
}
?>