What does PHP keyword 'var' do?

问题

This is probably a very trivial question, but I haven\'t been able to find the answer neither through web search engines, nor on php.net. Please just direct me to where I can read about this, if you haven\'t got time to explain.

1. What does the \'var\' keyword mean in PHP?
2. Are there any differences between PHP4 and PHP5?

回答1:

It's for declaring class member variables in PHP4, and is no longer needed. It will work in PHP5, but will raise an E_STRICT warning in PHP from version 5.0.0 up to version 5.1.2, as of when it was deprecated. Since PHP 5.3, var has been un-deprecated and is a synonym for 'public'.

Example usage:

class foo {
    var $x = 'y'; // or you can use public like...
    public $x = 'y'; //this is also a class member variables.
    function bar() {
    }
}

回答2:

The var keyword is used to declare variables in a class in PHP 4:

class Foo {
    var $bar;
}

With PHP 5 property and method visibility (public, protected and private) was introduced and thus var is deprecated.

回答3:

I quote from http://www.php.net/manual/en/language.oop5.visibility.php

Note: The PHP 4 method of declaring a variable with the var keyword is still supported for compatibility reasons (as a synonym for the public keyword). In PHP 5 before 5.1.3, its usage would generate an E_STRICT warning.

回答4:

Answer: From php 5.3 and >, the var keyword is equivalent to public when declaring variables inside a class.

class myClass {
  var $x;
}

is the same as (for php 5.3 and >):

class myClass {
  public $x;
}

History: It was previously the norm for declaring variables in classes, though later became depreciated, but later (PHP 5.3) it became un-depreciated.

回答5:

So basically it is an old style and do not use it for newer version of PHP. Better to use Public keyword instead;if you are not in love with var keyword. So instead of using

class Test {
    var $name;
}

Use

class Test {
   public $name;
}

回答6:

var is used like public .if a varable is declared like this in a class var $a; if means its scope is public for the class. in simplea words var ~public

var $a;
public

回答7:

here and now in 2018 using var for variable declaration is synonymous with public as in

class Sample{
    var $usingVar;
    public $usingPublic;

    function .....

}

回答8:

In PHP7.3 still working...

https://www.php.net/manual/en/language.oop5.visibility.php

If declared using var, the property will be defined as public.

来源：https://stackoverflow.com/questions/1206105/what-does-php-keyword-var-do