A tutorial network PHP introductory Tutorial 05:php variables

Source: Internet
Author: User

What is a PHP variable?

A variable is a container for storing information;

Second, the grammatical format

$ variable name = 1;

Three, PHP variable rules

1. The variable begins with the $ symbol, followed by the name of the variable;

2. The variable name must begin with a letter or an underscore;

3, variable name can not start with the number;

4. Variable names can only contain letters, numbers, characters, and underscores (A-Z, 0-9, and _)

5, variable name sensitivity to case ($y and $Y are two different variables)

6, Notice

For example, you enter the following code in PHP:

<?php

$a = $b = $c =wode;

$d = $b + $c;

Echo $d;

Entering "localhost" in the browser will eject an error as shown in the following illustration.

This error resolution:

First step: Open the configuration file in Phpstudy

Step Two: Search the error_reporting in the document with the shortcut key (ctrl+f), and put it behind E_all | E_strict changed to e_all& ' E_notice.

Step three: Restart the Phpstudy, the error message will not be displayed after refreshing the browser.

7, the variable can be declared together, said, as follows;

$a = $b = $c = 2;

echo $a, $b, $c;

Four, PHP variable example description

<?php

$x = 5;

$y = 6;

$z = $x + $y;

Echo $z;

?>

In the above example, $x = 3;   $y = 4; $z = $x + $y; Are all used in the syntax of variables, the above variables are similar to algebra, as follows.

X=5 y=6 Z=x+y

In algebra we use letters (such as x) to hold values (such as 5).

From the expression z=x+y above, we can calculate that the value of Z is 11.

In PHP, these three letters (X,Y,Z) are called variables.

V. Scope of PHP variables

PHP has four different scope of variables:

    • Local

    • Global

    • Static

    • Parameter

Local and global scopes

A variable declared outside of a function owns the Global scope and can only be accessed outside of the function.

Variables declared within a function have a local scope and can only be accessed within a function.

The following example tests variables with local and global scope:

<?php

$x = 5; Global variables

function MyTest ()

{

$y =10;//Local Variables

echo "<p> test variables are:<p> inside functions";

echo "Variable x is: $x";

echo "<br>";

echo "Variable y is: $y";

}

MyTest ();

echo "<p> test variables outside the function:<p>";

echo "Variable x is: $x";

echo "<br>";

echo "Variable y is: $y";

?>

To call a global variable defined outside of a function within a function, we need to add the global keyword before the variable in the function:

<?php

$x = 5;

$y = 10;

function MyTest ()

{

Global $x, $y;

$y = $x + $y;

}

MyTest ();

echo $y;//Output 15

?>

PHP stores all global variables in an array named $GLOBALS [index].

The name of the index save variable.

This array can be accessed within the function, or it can be used directly to update global variables.

<?php

$x = 5;

$y = 10;

function MyTest ()

{

$GLOBALS [' y ']= $GLOBALS [' x ']+ $GLOBALS [' Y '];

}

MyTest ();

Echo $y;

?>

Static Scope

When a function completes, all its variables are usually deleted. However, sometimes you want a local variable not to be deleted, you can use the static keyword

<?php

function MyTest ()

{

static $x = 0;

echo $x;

$x + +;

}

MyTest ();

MyTest ();

MyTest ();

?>

Parameter scopes

A parameter is a local variable that passes a value to a function by calling code.

Parameters are declared in the parameter list as part of the function declaration:

<?php

function MyTest ($x)

{

echo $x;

}

MyTest (5);

?>

The above is the entire content of PHP variables, I hope to help you learn.

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