PHP Flashcards
What array holds the values of submitted form parameters?
$_POST
How to get the URL of the current page (without protocol or hostname).
$_SERVER[PHP_SELF]
eg:
/users/enter.php
What does $_SERVER[PHP_SELF] return
The URL of the current page (without protocol or hostname).
eg:
/users/enter.php
What are the start and end tags of PHP. What are they for?
< ? 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.
Can a PHP program have multiple start and end tag pairs?
Yes
Is there only one start php tag?
No, you can also use < ? but support depends on the engine.
Are php keywords case-sensitive?
No, language keywords and function names are not case-sensitive. Variable names ARE! Best practice is to assume everything is.
What is the single-line commenting style?
Either // or #
Does php offer native Unicode support?
No, a string in php is a sequence of bytes and hence only natively supports a 256-character set.
Quotes used to surround a string are technically called…
delimiters
To concatenate two strings?
. (period) operator
What is the exponentiation operator?
**
What is the modulus division operator?
%
Can you use a dash in variable names in PHP?
No, only underscore.
How do you interpolate variables into a string?
“Hello, ${name}”
Use double-quotes. Braces aren’t necessary for this simple example, but prefer them always.
What is truthy / falsy in PHP?
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…)
How to avoid accidentally using = (assignment) instead of == (equality)?
Always put the variable name on the right and assignment will cause a parse error:
if (12 = $myvar) { … }
What is the spaceship operator?
<=> 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.
Each element of an array has a … and a …
key and a value.
An array key can be…
…any unique scalar value.
Syntax to create an array
$nums = array(1, 2, 3, 4);
or
$veggies = array(‘corn’ => ‘yellow’, ‘beet’ => ‘red’);
Shortcut for array() construct…
$arr = [0 => ‘zero’, 1 => ‘one’];
How to append to an array?
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] $arr[] = 'lunch';
How to get the number of elements in an array?
The count() function: count($arr);
What function checks for existence of a certain key in an array?
array_key_exists(‘key’) returns a boolean
What function checks for existence of a certain value in an array?
in_array(value, $arr) returns a boolean (is case sensitive)
What function finds the given value in an array?
array_search(value, $arr) returns the key of found value.
To remove an element from an array?
Use:
unset($arr[key]);
Easiest way to convert an array to string?
implode(‘, ‘, $arr);
Counterpart to the ‘implode’ function?
explode() breaks a string apart into an array given a delimiter.
Difference between iterating over an array using for vs foreach
foreach visits array elements in the order in which they were created - which isn’t necessarily sequentially by the keys.
