PHP Flashcards

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PHP is a popular scripting language created by Rasmus Lerdorf. It is a language particularly suited for creating dynamic websites and web applications. PHP is characterized by its simple syntax and ease of integration with HTML, allowing for the efficient creation of both simple pages and complex web systems. This language offers extensive support for databases and internet protocols, providing developers with tools for quickly creating functional server-side applications while maintaining flexibility and performance in handling HTTP requests.

Our flashcard app includes carefully selected PHP interview questions with comprehensive answers that will effectively prepare you for any interview requiring PHP knowledge. IT Flashcards is not just a tool for job seekers - it's a great way to reinforce and test your knowledge, regardless of your current career plans. Regular use of the app will help you stay up-to-date with the latest PHP trends and keep your skills at a high level.

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What are the main data types in PHP?

In PHP, we have eight main data types, which can be divided into three main categories: scalar, compound, and special.

1. Scalar types:
- Boolean: Stores true or false. Used for controlling conditions.
- Integer: Stores whole numbers.
- Float (or double): Stores real, floating-point numbers.
- String: Stores a string of characters.

2. Compound types:
- Array: Stores multiple values in one variable.
- Object: Stores instances of classes.

3. Special types:
- Resource: Stores references to external resources (e.g. files, database connections).
- NULL: Stores the special NULL value, which means "no value" or "unknown".

In addition to these, there is also the callable type, used for storing references to functions.

How to display text on a page in PHP?

In PHP, text can be displayed on the page using various commands, such as "echo", "print" or "printf".

Echo is a basic command used to display text. It is used to display strings, variables, arrays, etc.

Here is an example of using the echo command to display text:

<?php
echo "Hello world!";
?>

An alternative to "echo" is "print". Although "print" and "echo" serve the same purpose, there are some differences between them. "Print" returns a value of 1 (which means true), while "echo" does not return any value.

Example of using the print command to display text:

<?php
print "Hello world!";
?>

Another way to display text is to use "printf", which allows for formatting of the string before print.

Example of using "printf":

<?php
printf("Hello %s!", "world");
?>

In this case, %s is a placeholder that will be replaced by the string provided as the second argument to the printf function.

What is a variable in PHP and how can it be declared?

A variable in PHP is a location that holds a value. It acts as a container for storing data, such as numbers, strings, arrays, or objects, which can be used and modified during the script execution. The value stored in a variable depends on what has been assigned to it.

Variables in PHP begin with a dollar sign ($), followed by the variable name. The name must start with a letter or an underscore. A variable name in PHP cannot contain spaces. A variable in PHP is declared when you assign a value to it.

Example of declaring a variable in PHP:

$myVariable = 'Hello, World!';

In the above example, a variable named $myVariable has been declared and assigned the value 'Hello, World!'. This value is now stored in the $myVariable and can be used anywhere in the code that has access to it. Also, remember that PHP is a dynamically-typed language, meaning that the type of the variable is determined by the interpreter at runtime, based on the value we give to it.

How can you concatenate two strings in PHP?

In PHP, two strings can be concatenated using the . operator or by using a concatenate function. The . operator appends one string to the end of another.

Example:

$firstString = 'Hello';
$secondString = 'World';
$combinedString = $firstString . ' ' . $secondString;
echo $combinedString;  //Will output 'Hello World'

We can also use a concatenate function to join strings. However, this function is not built into PHP and must be written by the developer.

Example:

function concatenate($string1, $string2) {
    return $string1 . ' ' . $string2;
}
echo concatenate('Hello', 'World');  //Will output 'Hello World'

Both methods are often used in PHP to concatenate different strings, for example to generate content displayed on a page.