PHP Foundation - Questions

PHP is a recursive acronym for PHP: Hypertext Preprocessor. Learn more in Introduction to PHP.

PHP is a backend technology that helps us in building the server-side logic of web applications. Learn more in Introduction to PHP.

Rasmus Lerdorf is the one who created the PHP language. Back then, when he released its very first version in mid 1995, it was completely different from the PHP that we all know of and use today. Learn more in Introduction to PHP.

In the year 1995. Learn more in Introduction to PHP.

PHP being a 'scripting' language means that it runs inside a virtual environment, also known as an engine or implementation, that is simply a program coded in another computer language that is capable of parsing and executing PHP code. Learn more in Introduction to PHP.

PHP being a 'high-level' language means that it abstracts away many of the complexities of programming a computer machine and, instead, provides us with a very simple and easy-to-understand English-like syntax to code in. Learn more in Introduction to PHP.

An implementation of PHP simply refers to a computer program that is capable of parsing and converting PHP code into another format or executing it right after the parsing. Learn more in Introduction to PHP.

Zend Engine, written in C. Learn more in Introduction to PHP.

HHVM, PeachPie, Parrot. Learn more in Introduction to PHP.

Procedural, object-oriented and functional. Learn more in Introduction to PHP.

.php is the extension of a PHP file. Learn more in PHP First Program.

No. If we have a file called program.txt that contains PHP code and then try executing it, the PHP engine won't complain at all. Learn more in PHP First Program.

They denote PHP code in a PHP file. Learn more in PHP First Program.

The echo keyword is a means of outputting text to the standard output stream in PHP. Learn more in PHP First Program.

A string is a sequence of characters that denotes literal text in a program. Learn more in PHP First Program.

Using a pair of single quotes (''). Learn more in PHP First Program.

php.exe is an executable program that is meant to parse and execute PHP code. Sometimes it's also referred to as the PHP interpreter, or the PHP engine. Learn more in PHP First Program.

A string is a sequence of characters that denotes literal text in a program. Learn more in PHP Basics — Strings.

Using a pair of single quotes ('') and a pair of double quotes (""). Learn more in PHP Basics — Strings.

We can't have escape sequences inside single-quoted strings besides \' (to denote ' characters) and \\ (to denote \ characters) — everything inside a single-quoted string is, more or less, parsed literally. In contrast, in double-quoted strings, we can have a wide variety of escape sequences and they also support interpolation. Learn more in PHP Basics — Strings.

Yes. It's perfectly valid to do so.

<?php

$str = 'Single-quoted strings in PHP
can span
multiple lines';

<?php

$str = "Double-quoted strings in PHP
can also span
multiple lines";

Learn more in PHP Basics — Strings.

An esacpe sequence denotes a special character in a string. It begins with the backslash (\) symbol and is followed by a character to, as a whole, represent the special character. An example is \n, used to denote a newline character. Learn more in PHP Basics — Strings.

Here are some escape sequences: \n, \t, \r, \\, \', \". Learn more in PHP Basics — Strings.

A newline character. Learn more in PHP Basics — What are escape sequences?

An operator is basically a symbol or a keyword that performs an operation over one or more given values. An example is the arithmetic addition operator, denoted as +, that adds two numbers together. Learn more in PHP Basics — What is an operator?

String concatenation refers to joining together two strings into one single string. Learn more in PHP Basics — Strings.

The period (.) symbol. Learn more in PHP Basics — Strings.

Integers are whole numbers, i.e. numbers without a fractional part. Examples are 1, 2, 3, 1000, -5, -50, etc.

Floats, or floating-point numbers, are numbers with a fractional part. Examples include 1.0 (the fractional part is zero but there is one and so the number is a float), 2.45, 3.00000001, 1000.5, -5.111, -50.2478, etc.

Yes, this is true. Learn more in PHP Basics — Numbers.

Here are all the the six arithmetic operators of PHP: addition (+), subtraction (-), multiplication (*), division (/), exponentiation (**) and modulo (%). Learn more in PHP Basics — Basic arithmetic.

It means that when both the multiplication (*) and the addition (+) operators exist in an operation, without any parentheses (()), multiplication would be performed first. For example, in the expression 2 * 5 + 10, multiplication would happen first and then addition, giving the result 20 (instead of 30 if addition was done first). Learn more in PHP Basics — Basic arithmetic.

By grouping it in a pair of parentheses (()). Learn more in PHP Basics — Basic arithmetic.

There are multiple ways of defining a variable. For example:

• A variable is a container for holding data.
• A variable is a name in a program, referring to a location in memory where data is stored.

Learn more in PHP Basics — Variables.

We begin with the $ symbol, followed by the name of the variable to create, followed by the = symbol, followed by the value to initialize the variable with. Learn more in PHP Basics — Variables.

It means that two variables with names having different cases are considered to be different. That is, $foo is different from $FOO, $Foo, $fOO, etc. Learn more in PHP Basics — Variables.

A semantic error is an error in the meaning of a program. The program might run to completion but not produce the correct output. Learn more in PHP Basics — What is a semantic error?

Standard input refers to the stream that is pointed to by the STDIN constant provided by PHP. Typically, standard input in a PHP CLI program is tied to input from the keyboard. Learn more in PHP Basics — Standard input.

A function represents a block of code that is executed whenever the function is called. Learn more in PHP Basics — What is a function?

fgets() is meant to read data from a given file. Learn more in PHP Basics — Standard input.

A constant behaves more or less like a variable, except for that once assigned a value, it can't be changed and that it doesn't begin with the $ character. Learn more in PHP Basics — What is a constant?

STDIN is a constant that points to the standard input stream in PHP. Learn more in PHP Basics — Standard input.

A prompt message, which is immediately followed by an input request, describes what is required to be input (and even gives a visual hint for this using characters such as > or :).

In the following code, the echo statement outputs a prompt message:

<?php

echo 'Enter your name> ';
$input = fgets(STDIN);

Learn more in PHP Basics — Standard input.

(int) string_value. Learn more in PHP Basics — Converting to an integer.

. Learn more in PHP Basics — Statements and expressions.

An expression is a unitary piece of code that resolves down to a single value. An expression can be composed of expressions itself. Learn more in PHP Basics — Statements and expressions.

A keyword is simply a word that has a special meaning associated with it. An example is echo. It doesn't represent a constant value in PHP; instead, it serves to output text to the standard output stream. Learn more in PHP Basics — Statements and expressions.

An expression statement is a statement that is merely an expression. If PHP expects a statement somewhere and we provide it with an expression, what we have now is an expression statement. Learn more in PHP Basics — Statements and expressions.

True. All expressions can act as statements. Learn more in PHP Basics — Statements and expressions.

False. Learn more in PHP Basics — Statements and expressions.

A syntax error is an error in the syntax of code. Learn more in PHP Basics — What is a syntax error?

Here are the rules for naming variables in PHP:

• Names can't begin with a digit. Hence, $2nd is wrong.
• Names can only contain alphanumeric characters (a-z, A-Z, 0-9) and the _ (underscore) character; nothing else.
• Names can't contain spaces. Hence, $first word is wrong.

As a side note, surprisingly, for people having experience of another programming language, variables in PHP can be named after keywords. For instance, the variable $for is perfectly valid in PHP even though there is a for keyword in the language.

Learn more in PHP Basics — Variables — Rules for naming variables.

For a long time, PHP has sticked to using the snake case convention, i.e. snake_case, for naming built-in functions. Learn more in PHP Basics — Variables.

This simply means that variables in PHP don't have fixed (static) types; instead, the data type of the value stored in a variable can change during the course of the program. Hence, we say that PHP is a dynamically-typed language. Learn more in PHP Basics — Variables — Dynamically-typed nature of PHP.

A 'variable variable' in PHP is a variable whose name is obtained using another variable. Learn more in PHP Basics — Variables — Variable variables.

Supposing the $name is a variable holding the value 'greeting' and $greeting is another variable holding the value 'Hello'. Then $$name is a variable variable which simply becomes $greeting and, thus, resolves down to 'Hello'. Learn more in PHP Basics — Variables — Variable variables.

Using the isset() function. Learn more in PHP Basics — Variables — Determining a variable's existence.

It returns false even for variables that exist albeit have their value as NULL. Learn more in PHP Basics — Variables — isset() checks for NULL.

var_dump() is used to print a value in PHP along with its type information. Learn more in PHP Basics — Variables — var_dump().

Comments are statements in a program that are ignored, i.e. they just don't get executed. Learn more in PHP Comments.

Let's give three uses of comments in programs: to explain code; to document code; and to test/debug given code. Learn more in PHP Comments.

Single-line comments and multi-line comments. Learn more in PHP Comments — How to comment?

Single-line comments are denoted using either # or //, whereas multi-line comments are denoted using /* */. Learn more in PHP Comments — How to comment?

Learn more in PHP Comments — Tips for writing comments.

A data type is a set of values along with the operations possible on those values. Learn more in PHP Data Types.

We have the following three classifications: scalar, compound, and special. Learn more in PHP Data Types — Classifications of data types.

We have 4 scalar data types: integers, floats, Booleans, and strings; 4 compound data types: arrays, objects, callables, and iterables; and 2 special data types: resources and NULL. Learn more in PHP Data Types — Classifications of data types.

Absolutely true. PHP has the customary two types for representing numbers in programming: integers and floats. 10 is an integer whereas 10.5 is a float. Learn more in PHP Data Types — Integers and PHP Data Types — Floats.

Absolutely true. Even though mathematically 10 and 10.0 are the same, with the presence of .0 in 10.0, it becomes a float, whereas 10 is an integer. Learn more in PHP Data Types — Integers and PHP Data Types — Floats.

Using the (int) typecast as follows: (int) $v. Learn more in PHP Data Types — Integers.

Using the is_int() function, providing the arbitrary value to it as an argument. Learn more in PHP Data Types — Integers.

Using the (float) typecast as follows: (float) $v. Learn more in PHP Data Types — Floats.

Using the is_float() function. Learn more in PHP Data Types — Floats.

It refers to the total number of characters in the string. Learn more in PHP Data Types — Strings.

Using the strlen() function. Learn more in PHP Data Types — Strings.

The index of a character simply refers to its position in the string. Indexes in PHP start at 0. Learn more in PHP Data Types — Strings.

Using bracket notation following the string value. Learn more in PHP Data Types — Strings.

Using the expression $str[1] as the second character's index is 1. Learn more in PHP Data Types — Strings.

We can either use the (string) typecast, as in (string) $v, or concatenate the value with an empty string, as in '' . $v. (There's even a third way and that's to use the strval() function). Learn more in PHP Data Types — Strings.

Using the is_string() function. Learn more in PHP Data Types — Strings.

A Boolean is a true or false value. Learn more in PHP Data Types — Booleans.

Using the typecast (bool), as in (bool) $v. (We can also use the boolval() function.)

Using the is_bool() function. Learn more in PHP Data Types — Booleans.

An array is an ordered sequence of elements. Learn more in PHP Data Types — Arrays.

An element of an array simply refers to one of the items stored in it. Learn more in PHP Data Types — Arrays.

An element's index refers to its position in the array.

It's called the array's length.

It's an array without any elements. An empty array in PHP is denoted as []. Learn more in PHP Data Types — Arrays.

An array literal in PHP is the direct — the 'literal' — representation of an array in source code. It's denoted using a pair of square brackets ([]). Learn more in PHP Data Types — Arrays.

The array_push() function can be used to add elements to the end of an array. Learn more in PHP Data Types — Arrays.

We get a warning because it's not meaningful to convert an array to a string in PHP. Learn more in PHP Data Types — Arrays.

Using the print_r() function.

Using the sort() function.

It means that the function modifies the original array. Learn more in PHP Data Types — Arrays.

Using the is_array() function.

The gettype() function is used to obtain the type of a given value in PHP, as a string. For example, gettype(10) returns the string 'integer'. Learn more in PHP Data Types — gettype().

False. gettype($v), where $v is a float, returns the string 'double'. This is for backwards-compatibility with older versions of PHP. Learn more in PHP Data Types — gettype().