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Web Technologies > PHP Functions > Flashcards

PHP Functions Flashcards

1
Q

Task: Replace a backslash with a forward slash

A

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

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2
Q

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

A 
if (file_exists($filename)) {
  // do stuff
}
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3
Q

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

A

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

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4
Q

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

A

$str = trim($string);

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5
Q

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

A

$array = explode(“:”, $input);

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6
Q

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

A

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

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7
Q

Task: Get all of the methods names from a class

A

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

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8
Q

Task: Convert all strings in an array to lowercase

A

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

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9
Q

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

A

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)

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10
Q

Task: Sort an array - keys don’t matter

A

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)

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11
Q

Task: Make the first letter in a string uppercase

A

string ucfirst ( string $str );

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12
Q

Task: Format a decimal number into thousands for nice display

A

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 = “,” )

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13
Q

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

A

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

glue could be ‘,’ to create a csv

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14
Q

Task: Make the first characters of a string lowercase.

A

string lcfirst ( string $str )

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15
Q

Task: Compare two strings for equality

A

int strcmp ( string $str1 , string $str2 )

Returns 0

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16
Q

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

A

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

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17
Q

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

A

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

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

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18
Q

Question: What is the issue with using parse_str?

A

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

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19
Q

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

A

int strcoll ( string $str1 , string $str2 )

NOTE: Not binary safe

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20
Q

Question: Which function is just an alias of implode?

A

join

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21
Q

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

A

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

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22
Q

Question: What function is an alias of rtrim?

A

chop

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23
Q

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

A

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

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24
Q

Question: What is the case insensitive version of str_replace?

A

str_ireplace

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25
Q

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

A

array fgetcsv ( resource $handle [, int $length = 0 [, string $delimiter = “,” [, string $enclosure = ‘”’ [, string $escape = “\” ]]]] )

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26
Q

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

A

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

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27
Q

Task: Convert data to a JSON format

A

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

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28
Q

Question: What does the JSON_NUMERIC_CHECK bitmask do?

A

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

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29
Q

Question: What does the JSON_FORCE_OBJECT bitmask do?

A

It encodes the array as an object

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30
Q

Question: What does JSON_PRETTY_PRINT do?

A

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

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31
Q

Task: Use a function to decode a string of JSON

A

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

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32
Q

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

A

The second parameter should be set to true

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33
Q

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?

A

null

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34
Q

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

A

int json_last_error ( void )

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35
Q

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?

A

string utf8_encode ( string $data )’

utf8_encode(json_encode($payload));

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36
Q

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

A

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

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37
Q

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

A

mixed array_shift ( array &$array )

38
Q

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

A

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

39
Q

Task: Obtain a backtrace for debugging purposes

A

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

40
Q

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

A

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).

41
Q

Question: Can you use multiple autoloaders?

A

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.

42
Q

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

A

bool method_exists ( mixed $object , string $method_name )

43
Q

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

A

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

44
Q

Task: Start a session in PHP

A

bool session_start ( void )

45
Q

Task: Log a user out of a session

A

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. )

46
Q

Task: Get the session id

A

string session_id ([ string $id ] )

47
Q

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

A

session_id() == ‘’

48
Q

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

A

boolean password_verify ( string $password , string $hash )

NOTE: The hash should have been created using password_hash

49
Q

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

A

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

50
Q

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

A

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

51
Q

Task: You need to set a cookie

A

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

52
Q

Question: What is the main catch when using setcookie?

A

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

53
Q

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

A

string urlencode ( string $str )

54
Q

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

A

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)

55
Q

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

A

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’);

56
Q

Task: Convert a domain name to idna ascii form

A

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

57
Q

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

A 
bool get_magic_quotes_gpc ( void )
NOTE: Always returns false as of PHP 5.4.0
58
Q

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

A

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

(NOTE: The double rr in strrpos)

59
Q

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

A

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

60
Q

Task: Remove any null elements from an array

A

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

61
Q

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

A

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

62
Q

Question: What is a lambda?

A

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.

63
Q

Question: What is an anonymous function?

A

A function without a name

64
Q

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

A

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

65
Q

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

A

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);
}
66
Q

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

A

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

67
Q

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

A

callable

68
Q

Task: Create a stream context

A 
resource stream_context_create ([ array $options [, array $params ]] )
NOTE: Options must be an associative array of arrays (i.e. $arr['wrapper']['options'])
69
Q

Task: Read a file and write contents into an array

A

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

70
Q

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

A

file_get_contents()

71
Q

Task: Read a file into a string

A

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

72
Q

Task: Initialise a curl handle

A

resource curl_init ([ string $url = NULL ] )

i.e. $cur = curl_init();

73
Q

Task: set the options on curl handle

A

bool curl_setopt ( resource $ch , int $option , mixed $value )

NOTE: You may have to call this multiple times to set multiple options.

74
Q

Task: Determine the similarity between two strings

A

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

75
Q

Question: What does PCRE stand for?

A

Perl Compatible Regular Expressions

76
Q

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

A

preg

I.e. preg_match - reg ex

77
Q

Task: Determine whether a string matches a given regex pattern

A

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

78
Q

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

A

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

79
Q

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

A

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

80
Q

Question: What is the difference between preg_match and preg_match_all?

A

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

81
Q

Task: Encode an image appropriately for storing in a database

A

string base64_encode ( string $data )

82
Q

Task: Determine the name of a file given a path

A

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

83
Q

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

A

int filemtime ( string $filename )

84
Q

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

A

mixed reset ( array &$array )

NOTE: Reset will return the first element in the aray

85
Q

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

A

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

86
Q

Task: Sort an array by key in reverse

A

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

87
Q

Task: Sum an array containing numerical elements?

A

number array_sum ( array $array )

88
Q

Task: Test for a scalar variable?

A

bool is_scalar ( mixed $var )

89
Q

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

A

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

range(4,16,4);

90
Q

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

A

bool shuffle ( array &$array )

91
Q

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

A

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

92
Q

Task: Decompress a gzip’d file

A

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

Web Technologies (35 decks)

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