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Em PHP, variáveis são identificadores usados para armazenar dados que podem ser manipulados durante a execução de um programa. Elas permitem que você armazene diferentes tipos de valores (como números, strings, arrays, etc.) e os utilize ao longo do código.
Regras e características das variáveis em PHP:
Início com um $: Toda variável em PHP começa com o símbolo de cifrão ($), seguido pelo nome da variável.
Exemplo: $nome, $idade.
Sensibilidade a maiúsculas e minúsculas: Variáveis em PHP diferenciam maiúsculas de minúsculas. Por exemplo, $idade e $Idade são variáveis diferentes.
Atribuição dinâmica de tipos: PHP é uma linguagem de tipagem dinâmica, o que significa que você não precisa declarar o tipo de dado da variável. O PHP identifica automaticamente o tipo com base no valor atribuído.
Exemplo:
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$nome = "Maria"; // String
$idade = 25; // Inteiro
$preco = 29.99; // Float
Regras para nomes de variáveis:
O nome da variável deve começar com uma letra ou sublinhado (_), seguido de letras, números ou sublinhados.
Não pode começar com números.
Nomes de variáveis não podem conter espaços.
Escopo: As variáveis em PHP têm diferentes escopos, que definem onde elas podem ser acessadas no código:
Local: Definidas dentro de funções e acessíveis apenas lá.
Global: Definidas fora de funções e acessíveis globalmente.
Superglobais: Variáveis globais pré-definidas pelo PHP, como $_GET, $_POST, $_SESSION, entre outras.
Exemplo básico de uso de variáveis em PHP:
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What is a preprocessor in PHP?
As it is, PHP does not have a preprocessor; it is a preprocessor that processes form variables and other environmental variables and prints HTML or general text.
All variables in PHP start with which symbol?
In PHP, all variables must the preceded by the dollar sign. Variable name must not contain any space as well.
How can you declare the variable in PHP?
Variables in PHP do not need to be declared like some languages (e.g. JavaScript). This is all that needs to be done to assign a variable: $variable = "Value";
How do you swap variables in PHP?
By using a third temporary variable. $tmp = $a; $a = $b; $b = $tmp;
When should globals be used in PHP?
Problem with using global variables in php is that they lose the the assigned value in a different php file. They only keep the global variable value in the php file in which they are declared. Instead of globals try and use $_SESSION or $_COOKIE to keep value intact across different php files in a project
What is a preprocessor in PHP?
As it is, PHP does not have a preprocessor; it is a preprocessor that processes form variables and other environmental variables and prints HTML or general text.
All variables in PHP start with which symbol?
In PHP, all variables must the preceded by the dollar sign. Variable name must not contain any space as well.
How do you represent a variable in PHP?
Variables in php begin with $ and are declared by the user. $str1 = "wiki"; would store "wiki" into the variable $str1
Why after installing PHP can it happen that you are able to run PHP functions but not to pass variables?
There are many things that can stop your variables from passing between your forms and your php scripts. One common reason is that your php configuration file is not configured to pass your form variables as globals, and instead passes them through the $_GET and $_POST superglobals. So, for example, if you form is as such: <form method="post"> <input name="whatever"> </form> Your php script would access the variable $whatever through the $_POST superglobal. $whatever = $_POST['whatever'];
How can you declare the variable in PHP?
Variables in PHP do not need to be declared like some languages (e.g. JavaScript). This is all that needs to be done to assign a variable: $variable = "Value";
How do you swap variables in PHP?
By using a third temporary variable. $tmp = $a; $a = $b; $b = $tmp;
When should globals be used in PHP?
Problem with using global variables in php is that they lose the the assigned value in a different php file. They only keep the global variable value in the php file in which they are declared. Instead of globals try and use $_SESSION or $_COOKIE to keep value intact across different php files in a project
How do you create static variables in PHP?
Use the "static" keyword to declare a static variable within a function like shown below. <?php function fun() { static $variable; static $another_variable = ''; } ?>
What is a super global class in PHP?
Super global variables are ones that PHP automatically makes available in any scope (i.e. no need to write "global $_GET" in your script, it's already global).
PHP case sensitivity refers to what?
PHP case sensitivity refers to that in coding it matters if the code is in capital letters. Case sensitivity specifically in PHP refers to variables, constants, array keys, class properties, and class constants. Some items in PHP that are not case sensitive are functions, class constructors, class methods, and keywords and constructs.
Where are variables displayed when using the POST method?
When data is POSTed to a PHP script, you may access them from the $_POST super global variable.
What is a php session?
A PHP session is a concept where specific variables (and their respective values) are carried throughout a user's viewing of a PHP-driven website. These sessions can be initialized and continued using the session_start() function. The session values are stored in the $_SESSION global variable. For more information, see the php.net documentation of session functions.
