PHP Set 9

Question 1

What is PDO?

Answer 1

PHP Data Object: An extension that defines a lightweight, consistent interface for accessing databases in PHP

Question 2

Why is PDO needed?

Answer 2

There are many database extensions that are similar but don’t provide the same interface

Question 3

What are the 3 classes provided by PDO?

Answer 3

1. PDO class: Represents a connection between PHP and a database server
2. PDOStatement class: Represents a prepared statement and an associated result set when the statement is executed
3. PDOException class: Represents an error raised by PDO

Question 4

How many drivers does PDO have for connecting to database systems?

Answer 4

12 sets of drivers to connect to different systems

Question 5

When should you used prepared APIs vs direct execution APIs when performing SQL queries?

Answer 5

Use prepared when SQL statements may contain user input, can use direct execution when it does not contain user input

Question 6

What are the 2 parameter methods for PDO prepared statements?

Answer 6

1. Named parameters:
   $tpl1 = “select slot from meetings
   where name = :name and email =
   :email”;
2. Positional parameters:
   $tpl2 = “select slot from meetings
   where name = ? and email = ?”;

Question 7

What is the syntax for the PDO prepare method?

Answer 7

PDO::prepare(string $query, array $options=[]): PDOStatement | False

Question 8

What is returned by the PDO prepare method?

Answer 8

Returns a PDOStatement object on success or FALSE on failure

Question 9

What is the syntax for the PDO bindValue method?

Answer 9

PDO::bindValue(string|int $param,
mixed $value, int $type =
PDO::PARAM_STR |
PDO::PARAM_INT):bool

Where:
$param is a parameter of the firm
:name for named parameters or the
1-indexed position of the parameter
for positional parameters
$value is the value to bind to the
specified parameter
$type is an explicit data type for the
parameter using the PDO::PARAM_*
constants

Question 10

What is the syntax for the PDO bindParam method?

Answer 10

bool PDO::bindParam(string|int
$param, mixed &$var, int $type =
PDO::PARAM_STR |
PDO::PARAM_INT, int $maxLength =
0, mixed $driverOptions =
null): bool

Where:
$param is a parameter of the firm
:name for named parameters or the
1-indexed position of the parameter
for positional parameters
$var is the name of the variable to
bind to the parameter
$type is an explicit data type for the
parameter using the PDO::PARAM_*
constants
$maxLength is an optional parameter
for the maximum length of the data
type
$driverOptions is optional

Question 11

How do you execute a PDO prepared statement?

Answer 11

Using the execute() method when parameters have been set using bindValue() or bindParam()

Question 12

What is the difference between bindValue() and bindParam()?

Answer 12

bindParam() binds a parameter exclusively to a specified variable name which is bound as a reference
bindValue() binds a value which could be a variable, integer, or string to a parameter

Question 13

What can you use as PHP debugging tools?

Answer 13

1. An online PHP interpreter
2. phpdpg the command line debugger
3. Xdebug which is an extension for PHP on VScode enabling step by step execution

Question 14

What are the functions that can be used to dump variables to standard output for debugging?

Answer 14

1. var_dump($var): Dumps the variable type and value to stdout
2. print_r($var) prints the variable value in human-readable form to stdout
3. get_defined_vars() gets all defined variables including built-ins and custom variables
4. debug_zval_dump($var) dumps the variable with its reference counts
5. debug_print_backtrace() prints a backtrace that shows the current function call chain
6. debug_backtrace() gets the backtrace. Handles traces from outside of functions

Question 15

What are the options that can be specified for switching error reporting level?

Answer 15

These must be set in php.ini
1. error_reporting sets the level of logging
2. display_errors tells PHP if and where to display error messages
3. display_startup_errors should only be used when debugging
4. log_errors and error_log work together to send errors to a specified log file. This should be done in production rather than displaying the logs to users