How to define variable in php

How to define a variable in php

Variables defined in this fashion are not accessible within functions without a global declaration in the function . This is useful if you are writing a library class and wish to let the user name it whatever they want, for example by setting a define in a config file.

How to defined a variable on PHP?

Clearly from the error can be read that the current index you are using for the array doesn’t exist.

$up_fonts[$font][‘style’] is not set.

You haven’t defined your array enough. Check if the value exist with

if (isset($up_fonts[$font]['style'])): $stylesheet = $up_fonts[$font]['style']; endif; 

You will need to add an isset conditional around your tags (or something similar to that effect)

if (isset($up_fonts[$font]['style'])) < // logic here. >

How to declare a global variable in php?, An associative array containing references to all variables which are currently defined in the global scope of the script. The variable names are the keys of the array. If you have a set of functions that need some common variables, a class with properties may be a good choice instead of a global:

How to declare a php class with a variable name

Sure, use php to write to a file with the name you want, then require that file. You could also use eval , e.g. something like: eval(«class $myname < . >;»);

For more complicated cases, use a library such as Zend’s CodeGenerator (example here).

Please don’t up/downvote this response or mark it as the answer.

Eugen Rieck’s answer is the best one, but got buried in the comments.

The answer he linked to shows how to use class_alias() to name a class to a define. This is useful if you are writing a library class and wish to let the user name it whatever they want, for example by setting a define in a config file.

So if you are writing a library containing MyLibraryClass, you could let the user name it to something like LC for conciseness so they can write LC::someFunction() or LC->someFunction instead of having to write the whole thing out.

Php — How define variable in laravel component, so how define variable in component that can be use in it ? Thanks. php variables components laravel-8. Share. Improve this question. Follow asked Nov 19, 2020 at 12:30. ebeliejinfren ebeliejinfren. 167 2 2 silver badges 14 14 bronze badges. 2.

Define a variable in a function php [duplicate]

You need to define $tab at the beginning of the function.

Or you could just add $tab = «»; as the first line of the function, now you are defining it outside the function which you should remove.

Then you need to do .= on the variable. The variable does not exist where you start using it.

«.=» is telling PHP to add a string to an existing variable. PHP cannot add the string if there is no existing variable.

// Add this before your first $tab .= $tab = NULL; 

Declaring Variable Types in PHP?, You can’t explicitly define a variable’s type in PHP, its type is decided by the context it is used in. Share. Improve this answer. Follow answered Dec 24, 2008 at 7:10. Paige Ruten Paige Ruten. 166k 36 36 gold badges 174 174 silver badges 195 195 bronze badges

How can I see a variable defined in another php-file?

I’m guessing you’re trying to use the global variables within a function body. Variables defined in this fashion are not accessible within functions without a global declaration in the function .

$foo = 'bar'; function printFoo() < echo "Foo is '$foo'"; //prints: Foo is '', gives warning about undefined variable >

There are two alternatives:

The other option, as Finbarr mentions, is to define a constant:

define('FOO', 'bar'); function printFoo() < echo "Foo is '" . FOO . "'"; //prints: Foo is 'bar' >

Defining has the advantage that the constant can’t be later overwritten.

See PHP define: http://php.net/manual/en/function.define.php

define("CONSTANT_NAME", "Constant value"); 

Accessed elsewhere in code with CONSTANT_NAME . If the values are constant, you are definitely best to use the define function rather than just variables — this will ensure you do not accidentally overwrite your variable constants.

That is exactly how it works.

Have you got error reporting set up, and is there anything in the error log? I’m guessing the include is failing but you’re not seeing the error.

PHP — Variable Types, Variables are assigned with the = operator, with the variable on the left-hand side and the expression to be evaluated on the right. Variables can, but do not need, to be declared before assignment. Variables in PHP do not have intrinsic types — a variable does not know in advance whether it will be used to store a number or a …

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PHP Variables

Summary: in this tutorial, you will learn how to use PHP variables to store data in programs.

Define a variable

A variable stores a value of any type, e.g., a string, a number, an array, or an object.

A variable has a name and is associated with a value. To define a variable, you use the following syntax:

$variable_name = value;Code language: PHP (php)

When defining a variable, you need to follow these rules:

• The variable name must start with the dollar sign ( $ ).
• The first character after the dollar sign ( $ ) must be a letter ( a-z ) or the underscore ( _ ).
• The remaining characters can be underscores, letters, or numbers.

PHP variables are case-sensitive. It means that $message and $Message variables are entirely different.

The following example defines a variable called $title :

 $title = "PHP is awesome!";Code language: HTML, XML (xml)

To display the values of variables on a webpage, you’ll use the echo construct. For example:

html> html lang="en"> head> meta charset="UTF-8"> meta name="viewport" content="width=device-width, initial-scale=1.0"> title>PHP Variables title> head> body>  $title = 'PHP is awesome!'; ?> h1> echo $title; ?> h1> body> html>Code language: HTML, XML (xml)

If you open the page, you’ll see the following message:

Another shorter way to show the value of a variable on a page is to use the following syntax:

= $variable_name ?>Code language: HTML, XML (xml)

For example, the following shows the value of the $title variable in the heading:

html> html lang="en"> head> meta charset="UTF-8"> meta name="viewport" content="width=device-width, initial-scale=1.0"> title>PHP Variables title> head> body>  $title = 'PHP is awesome!'; ?> h1>= $title; ?> h1> body> html>Code language: HTML, XML (xml)

Mixing PHP code with HTML will make the code unmaintainable, especially when the application grows. To avoid this, you can separate the code into separate files. For example:

• index.php – store the logic for defining and assigning value to variables.
• index.view.php – store the code that displays the variables.
• Use the require construct to include the code from the index.view.php in the index.php file.

The following shows the contents of the index.view.php file:

html> html lang="en"> head> meta charset="UTF-8"> meta name="viewport" content="width=device-width, initial-scale=1.0"> title>PHP Variables title> head> body> h1>= $title ?> h1> body> html>Code language: HTML, XML (xml)

And the following shows the contents of the index.php file:

 $title = 'PHP is awesome!'; require 'index.view.php';Code language: HTML, XML (xml)

If you open the index.php file on the web browser, you’ll see the same output.

By doing this, you separate the code responsible for logic and the code responsible for displaying the file. This is called the separation of concerns (SoC) in programming.

Summary

• A variable stores a value, and its name always starts with $ sign.
• Use the separation of concerns principle to separate the PHP logic from HTML.

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PHP Variables

In PHP, a variable starts with the $ sign, followed by the name of the variable:

Example

After the execution of the statements above, the variable $txt will hold the value Hello world! , the variable $x will hold the value 5 , and the variable $y will hold the value 10.5 .

Note: When you assign a text value to a variable, put quotes around the value.

Note: Unlike other programming languages, PHP has no command for declaring a variable. It is created the moment you first assign a value to it.

Think of variables as containers for storing data.

PHP Variables

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).

• A variable starts with the $ sign, followed by the name of the variable
• A variable name must start with a letter or the underscore character
• A variable name cannot start with a number
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
• Variable names are case-sensitive ( $age and $AGE are two different variables)

Remember that PHP variable names are case-sensitive!

Output Variables

The PHP echo statement is often used to output data to the screen.

The following example will show how to output text and a variable:

Example

The following example will produce the same output as the example above:

Example

The following example will output the sum of two variables:

Example

Note: You will learn more about the echo statement and how to output data to the screen in the next chapter.

PHP is a Loosely Typed Language

In the example above, notice that we did not have to tell PHP which data type the variable is.

PHP automatically associates a data type to the variable, depending on its value. Since the data types are not set in a strict sense, you can do things like adding a string to an integer without causing an error.

In PHP 7, type declarations were added. This gives an option to specify the data type expected when declaring a function, and by enabling the strict requirement, it will throw a «Fatal Error» on a type mismatch.

You will learn more about strict and non-strict requirements, and data type declarations in the PHP Functions chapter.

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