PHP Functions

Question 1

Task: Replace a backslash with a forward slash

Answer 1

$string = str_replace(‘\’, ‘/’, $string);

Question 2

Task: Determine if a given filename exists in the specified location

Answer 2

if (file_exists($filename)) {
  // do stuff
}

Question 3

Task: Use a function to filter a URL to make sure it’s safe

Answer 3

$url = filter_var($this->url, FILTER_SANITIZE_URL);

Question 4

Task: Write a function to remove the whitespace off the ends of a string.

Answer 4

$str = trim($string);

Question 5

Task: Given a string with colons as a separator, split the string up into components into an array.

Answer 5

$array = explode(“:”, $input);

Question 6

Task: Determine if a string exists in an array of srings

Answer 6

if (in_array($string, $array)) { // Do stuff }

Question 7

Task: Get all of the methods names from a class

Answer 7

$methods = get_class_methods($obj);
or
$methods = get_class_methods(‘className’);

Question 8

Task: Convert all strings in an array to lowercase

Answer 8

$yourArray = array_map(‘strtolower’, $yourArray);

Question 9

Task: Sort an array that has keys, without damaging the keys

Answer 9

bool uasort ( array &$array , callable $value_compare_func )

NOTE: $value_compare_func should do a test between the two values and return -1 or 1 (not much point in returning 0)

Question 10

Task: Sort an array - keys don’t matter

Answer 10

bool usort ( array &$array , callable $value_compare_func );

NOTE: $value_compare_func should test between two values and return -1 or 1 (not much point in returning 0)

Question 11

Task: Make the first letter in a string uppercase

Answer 11

string ucfirst ( string $str );

Question 12

Task: Format a decimal number into thousands for nice display

Answer 12

string number_format ( float $number [, int $decimals = 0 ] );

OR (note: only 1,2 or 4 parameters allowed)

string number_format ( float $number , int $decimals = 0 , string $dec_point = “.” , string $thousands_sep = “,” )

Question 13

Task: Create a string from an array, that is separated by a ‘glue’ string

Answer 13

string implode ( string $glue , array $pieces );

glue could be ‘,’ to create a csv

Question 14

Task: Make the first characters of a string lowercase.

Answer 14

string lcfirst ( string $str )

Question 15

Task: Compare two strings for equality

Answer 15

int strcmp ( string $str1 , string $str2 )

Returns 0

Question 16

Task: Parse a url, and return an associative array with it’s components

Answer 16

mixed parse_url ( string $url [, int $component = -1 ] );

Question 17

Task: Take a string and parse it like a URL, outputing the variable / value combinations into new variables

Answer 17

void parse_str ( string $str [, array &$arr ] )

NOTE: It does not return a value - it will write the values into new variables

Question 18

Question: What is the issue with using parse_str?

Answer 18

If you don’t pass an array as the second argument, values are written to the current context, and could overwrite values. Using an array means they are written to the array

Question 19

Task: Which function would you use to compare two strings and ensure it takes into account the current locale?

Answer 19

int strcoll ( string $str1 , string $str2 )

NOTE: Not binary safe

Question 20

Question: Which function is just an alias of implode?

Answer 20

join

Question 21

Task: You need to cut whitespace or other characters from the end of a string.

Answer 21

string rtrim ( string $str [, string $character_mask ] )

Question 22

Question: What function is an alias of rtrim?

Answer 22

chop

Question 23

Task: You have to parse a comma seperated string into an array?

Answer 23

array str_getcsv ( string $input [, string $delimiter = “,” [, string $enclosure = ‘”’ [, string $escape = “\” ]]] )

Question 24

Question: What is the case insensitive version of str_replace?

Answer 24

str_ireplace

Question 25

Task: read a single line of a file and write the contents into an array

Answer 25

array fgetcsv ( resource $handle [, int $length = 0 [, string $delimiter = "," [, string $enclosure = '"' [, string $escape = "\\" ]]]] )

Question 26

Question: What needs to be done before fgetcsv can be used?

Answer 26

A file must be opened using fopen (it requires a file handle)

Question 27

Task: Convert data to a JSON format

Answer 27

string json_encode ( mixed $value [, int $options = 0 [, int $depth = 512 ]] )

Question 28

Question: What does the JSON_NUMERIC_CHECK bitmask do?

Answer 28

Checks for a string being a number, if so will encode it as a number (so not as a string)

Question 29

Question: What does the JSON_FORCE_OBJECT bitmask do?

Answer 29

It encodes the array as an object

Question 30

Question: What does JSON_PRETTY_PRINT do?

Answer 30

It formats the output of json_encode in an easy to read manner (useful really only for debugging since it adds overhead)

Question 31

Task: Use a function to decode a string of JSON

Answer 31

mixed json_decode ( string $json [, bool $assoc = false [, int $depth = 512 [, int $options = 0 ]]] )

Question 32

Question: What parameter do you set on json_decode to return an associative array instead of an object?

Answer 32

The second parameter should be set to true

Question 33

Question: If a document is 3 levels deep, and you specify a max of 2 levels of recursion - what is returned, the first two levels or null?

Answer 33

null

Question 34

Task: Use a function to determine what the last error was from a json decode or encode

Answer 34

int json_last_error ( void )

Question 35

Task: The datasource is not under your control and you want to make sure the output of json_encode is UTF-8 compliant (or you will raise a JSON_ERROR_UTF8 when decoding) What function do you use to ensure UTF-8 encoding?

Answer 35

string utf8_encode ( string $data )' utf8_encode(json_encode($payload));

Question 36

Task: Use a built in php function to configure an error handler function.

Answer 36

mixed set_error_handler ( callable $error_handler [, int $error_types = E_ALL | E_STRICT ] )

Question 37

Task: Remove and return the start of the array (i.e. element 0)

Answer 37

mixed array_shift ( array &$array )

Question 38

Question: What operator should you use to test the return value of file_get_contents

Answer 38

the === operator. This is because it may return boolean false, but may also return a value that evaluates to false.

Question 39

Task: Obtain a backtrace for debugging purposes

Answer 39

array debug_backtrace ([ int $options = DEBUG_BACKTRACE_PROVIDE_OBJECT [, int $limit = 0 ]] )

Question 40

Task: Use php's own logging system to write an error to the logs.

Answer 40

bool error_log ( string $message [, int $message_type = 0 [, string $destination [, string $extra_headers ]]] ) NOTE: You can use message_type=1 to send an email, you would then need to provide extra_headers (just like PHP's mail function).

Question 41

Question: Can you use multiple autoloaders?

Answer 41

Yes - PHP will allow multiple autoloaders to be registered. When one fails to find a file, then it tries the next - therefore do NOT throw an error in an autoloader.

Question 42

Task: Determine, in a single function call whether a method is present on an object?

Answer 42

bool method_exists ( mixed $object , string $method_name )

Question 43

Question: If you use method_exists, and the class you pass to it doesn't happen, will it use the autoloader?

Answer 43

Yes, it will use any registered auto loaders to find the class referenced.

Question 44

Task: Start a session in PHP

Answer 44

bool session_start ( void )

Question 45

Task: Log a user out of a session

Answer 45

bool session_destroy(void) (NOTE: This doesn't actually log the user out - it's a step in the process. You also have to unset variables associated with the session and delete any cookies, and unset the session id. )

Question 46

Task: Get the session id

Answer 46

string session_id ([ string $id ] )

Question 47

Question: What function would you use to test if a session already exists?

Answer 47

session_id() == ''

Question 48

Task: You have a hashed password, and you want to verify that a string entered by a user matches, what function do you use?

Answer 48

boolean password_verify ( string $password , string $hash ) NOTE: The hash should have been created using password_hash

Question 49

Task: You need to generate a hash for a password - what should you use?

Answer 49

string password_hash ( string $password , integer $algo [, array $options ] )

Question 50

Question: In the past it was common practise to provide a salt when creating hashed passwords. Should you do this when using password_hash?

Answer 50

No - the intended (and safest) mode of operation is to use password_hash with the default salt.

Question 51

Task: You need to set a cookie

Answer 51

bool setcookie ( string $name [, string $value [, int $expire = 0 [, string $path [, string $domain [, bool $secure = false [, bool $httponly = false ]]]]]] )

Question 52

Question: What is the main catch when using setcookie?

Answer 52

The data must be sent prior to ANY output from your page (including html and head tags)

Question 53

Task: Convert a string into a value safe for making part of a url

Answer 53

string urlencode ( string $str )

Question 54

Task: Validate that the domain of an email address is valid

Answer 54

bool checkdnsrr ( string $host [, string $type = "MX" ] ) NOTE: This function takes other 'type's', such as A, MX, NS, SOA, PTR, CNAME, AAAA etc (basically dns record types)

Question 55

Question: What is the issue with simply relying on the result of checkdnsrr?

Answer 55

Some domains can have special characters in them (especially ones in Europe) - you need to convert the domain to ascii first. checkdnsrr(idn_to_ascii('ñandu.cl'), 'A');

Question 56

Task: Convert a domain name to idna ascii form

Answer 56

string idn_to_ascii ( string $domain [, int $options = 0 [, int $variant = INTL_IDNA_VARIANT_2003 [, array &$idna_info ]]] )

Question 57

Task: How would you determine if magic quotes was enabled on your system?

Answer 57

``` bool get_magic_quotes_gpc ( void ) NOTE: Always returns false as of PHP 5.4.0 ```

Question 58

Task: Find the last occurrence of a substring in a string.

Answer 58

int strrpos ( string $haystack , string $needle [, int $offset = 0 ] ) (NOTE: The double rr in strrpos)

Question 59

Task: Find the first occurrance of a substring in a string.

Answer 59

mixed strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )

Question 60

Task: Remove any null elements from an array

Answer 60

array array_filter ( array $array [, callable $callback ] )

Question 61

Question: The function includes returns a value, what is it, and how do you make it return something more useful?

Answer 61

It returns 1 if the include was successful, however, if the file has a return statement in it, it will return that value.

Question 62

Question: What is a lambda?

Answer 62

It is an anonymous function that can be assigned to a variable or passed to another function as an argument. It is useful for callbacks, and when we don't want to create a function that is used only once and pollutes the global namespace.

Question 63

Question: What is an anonymous function?

Answer 63

A function without a name

Question 64

Question: What is the difference between a lambda and a closure?

Answer 64

They are essentially the same, however a closure can access variables outside the scope of the function (via the 'use' keyword)

Question 65

Question: What is the test for a closure in PHP (i.e. how do we tell if it is indeed a closure?)

Answer 65

If it is an object, and it is callable (closures are objects in PHP and they implement __invoke) ``` function is_closure($t) { return is_object($t) && ($t instanceof Closure); } ```

Question 66

Task: Apply a function (closure or lamdba) to each element in an array

Answer 66

bool array_walk ( array &$array , callable $callback [, mixed $userdata = NULL ] )

Question 67

Question: What kind of type hinting can be used to ensure a variable passed to a function is a lambda / closure?

Answer 67

callable

Question 68

Task: Create a stream context

Answer 68

``` resource stream_context_create ([ array $options [, array $params ]] ) NOTE: Options must be an associative array of arrays (i.e. $arr['wrapper']['options']) ```

Question 69

Task: Read a file and write contents into an array

Answer 69

array file ( string $filename [, int $flags = 0 [, resource $context ]] )

Question 70

Question: file will read the contents of a file into an array, what function would you use to write a file into a string?

Answer 70

file_get_contents()

Question 71

Task: Read a file into a string

Answer 71

string file_get_contents ( string $filename [, bool $use_include_path = false [, resource $context [, int $offset = -1 [, int $maxlen ]]]] )

Question 72

Task: Initialise a curl handle

Answer 72

resource curl_init ([ string $url = NULL ] ) i.e. $cur = curl_init();

Question 73

Task: set the options on curl handle

Answer 73

bool curl_setopt ( resource $ch , int $option , mixed $value ) NOTE: You may have to call this multiple times to set multiple options.

Question 74

Task: Determine the similarity between two strings

Answer 74

int similar_text ( string $first , string $second [, float &$percent ] )

Question 75

Question: What does PCRE stand for?

Answer 75

Perl Compatible Regular Expressions

Question 76

Question: What prefix do functions in PHP that deal with PCRE start with?

Answer 76

preg | I.e. preg_match - reg ex

Question 77

Task: Determine whether a string matches a given regex pattern

Answer 77

int preg_match ( string $pattern , string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] )

Question 78

Task: Split a string at the point where a regex matches

Answer 78

array preg_split ( string $pattern , string $subject [, int $limit = -1 [, int $flags = 0 ]] )

Question 79

Question: preg_split splits a string using a regex, is the pattern included in the output?

Answer 79

No - if the pattern is a straight work for example, ('i.e. "is"') - the strings either side will be returned, but not the pattern itself

Question 80

Question: What is the difference between preg_match and preg_match_all?

Answer 80

preg_match_all will return (through the array) all of the matches, not just the first.

Question 81

Task: Encode an image appropriately for storing in a database

Answer 81

string base64_encode ( string $data )

Question 82

Task: Determine the name of a file given a path

Answer 82

string basename ( string $path [, string $suffix ] )

Question 83

Task: Determine the date / time of the last file modification?

Answer 83

int filemtime ( string $filename )

Question 84

Task: Reset an arrays internal pointer to the first element.

Answer 84

mixed reset ( array &$array ) NOTE: Reset will return the first element in the aray

Question 85

Task: Run a function over each element in an array in a recursive function

Answer 85

bool array_walk_recursive ( array &$array , callable $callback [, mixed $userdata = NULL ] )

Question 86

Task: Sort an array by key in reverse

Answer 86

bool krsort ( array &$array [, int $sort_flags = SORT_REGULAR ] )

Question 87

Task: Sum an array containing numerical elements?

Answer 87

number array_sum ( array $array )

Question 88

Task: Test for a scalar variable?

Answer 88

bool is_scalar ( mixed $var )

Question 89

Task: Create an array with numbers between 4 and 16 that are divisible by 4 (in one function, no control statements)

Answer 89

array range ( mixed $start , mixed $end [, number $step = 1 ] ) range(4,16,4);

Question 90

Task: Take an array and randomise the elements within it.

Answer 90

bool shuffle ( array &$array )

Question 91

Task: Split a string either into characters or at a specific point in a string

Answer 91

array str_split ( string $string [, int $split_length = 1 ] )

Question 92

Task: Decompress a gzip'd file

Answer 92

string gzuncompress ( string $data [, int $length = 0 ] )