PHP

Question 1

What array holds the values of submitted form parameters?

Answer 1

$_POST

Question 2

How to get the URL of the current page (without protocol or hostname).

Answer 2

$_SERVER[PHP_SELF]
eg:
/users/enter.php

Question 3

What does $_SERVER[PHP_SELF] return

Answer 3

The URL of the current page (without protocol or hostname).
eg:
/users/enter.php

Question 4

What are the start and end tags of PHP. What are they for?

Answer 4

< ? php and ? >

The PHP engine ignores anything outside of those tags.. You can leave off the end tag at the end of a PHP file.

Question 5

Can a PHP program have multiple start and end tag pairs?

Answer 5

Yes

Question 6

Is there only one start php tag?

Answer 6

No, you can also use < ? but support depends on the engine.

Question 7

Are php keywords case-sensitive?

Answer 7

No, language keywords and function names are not case-sensitive. Variable names ARE! Best practice is to assume everything is.

Question 8

What is the single-line commenting style?

Answer 8

Either // or #

Question 9

Does php offer native Unicode support?

Answer 9

No, a string in php is a sequence of bytes and hence only natively supports a 256-character set.

Question 10

Quotes used to surround a string are technically called…

Answer 10

delimiters

Question 11

To concatenate two strings?

Answer 11

. (period) operator

Question 12

What is the exponentiation operator?

Answer 12

**

Question 13

What is the modulus division operator?

Answer 13

%

Question 14

Can you use a dash in variable names in PHP?

Answer 14

No, only underscore.

Question 15

How do you interpolate variables into a string?

Answer 15

“Hello, ${name}”

Use double-quotes. Braces aren’t necessary for this simple example, but prefer them always.

Question 16

What is truthy / falsy in PHP?

Answer 16

This is called an expression’s ‘truth value.’
There are only seven specific results that evaluate to false.
All integers and floating-point values (except 0 and 0.0) are true.
All strings (except empty string “” and “0”) are true.
The special constants false and null also evaluate to false.
An empty array is false.
(There are also empty SimpleXML objects and -0 and -0.0, but let’s keep it simple…)

Question 17

How to avoid accidentally using = (assignment) instead of == (equality)?

Answer 17

Always put the variable name on the right and assignment will cause a parse error:
if (12 = $myvar) { … }

Question 18

What is the spaceship operator?

Answer 18

<=> works like strcmp(), but for any data type.
Evaluates to a negative number when its lefthand operand is less than the righthand operand, a positive number when the righthand operand is bigger, and 0 when they are equal.

Question 19

Each element of an array has a … and a …

Answer 19

key and a value.

Question 20

An array key can be…

Answer 20

…any unique scalar value.

Question 21

Syntax to create an array

Answer 21

$nums = array(1, 2, 3, 4);
or
$veggies = array(‘corn’ => ‘yellow’, ‘beet’ => ‘red’);

Question 22

Shortcut for array() construct…

Answer 22

$arr = [0 => ‘zero’, 1 => ‘one’];

Question 23

How to append to an array?

Answer 23

Empty brackets append to an array. If the array doesn’t exist yet, element is added at key 0.

// set $arr[0]
$arr[] = 'breakfast';

// set $arr[1]
$arr[] = 'lunch';

Question 24

How to get the number of elements in an array?

Answer 24

The count() function:
count($arr);

Question 25

What function checks for existence of a certain key in an array?

Answer 25

array_key_exists(‘key’) returns a boolean

Question 26

What function checks for existence of a certain value in an array?

Answer 26

in_array(value, $arr) returns a boolean (is case sensitive)

Question 27

What function finds the given value in an array?

Answer 27

array_search(value, $arr) returns the key of found value.

Question 28

To remove an element from an array?

Answer 28

Use:

unset($arr[key]);

Question 29

Easiest way to convert an array to string?

Answer 29

implode(‘, ‘, $arr);

Question 30

Counterpart to the ‘implode’ function?

Answer 30

explode() breaks a string apart into an array given a delimiter.

Question 31

Difference between iterating over an array using for vs foreach

Answer 31

foreach visits array elements in the order in which they were created - which isn’t necessarily sequentially by the keys.