PHP Static Properties

PHP - Static Properties

The static keyword also creates static properties.

You can read a static property directly, without ever making an object from its class.

Declare a Static Property

Declaring a static property works by adding the static keyword to it:

Static property declaration syntax

static goes ahead of the property name:

<?php
class ClassName {
  public static $statProp = "PromptCookbook";
}
?>

Access a Static Property

Reading a static property takes three parts: the class name, a double colon (::), and the property name.

The next example declares a static property called $value and echoes it directly in that form. No object is needed:

Example

Read a static property through its class name:

Create a PHP class called pi with a public static property $value set to 3.14159. Echo the static property directly using the class name.

> Output: PHP script

Prompt

Create a PHP class called pi with a public static property $value set to 3.14159. Echo the static property directly using the class name.

Output: PHP script

<?php
class pi {
  // static property
  public static $value = 3.14159;
}

// Get static property directly
echo pi::$value;
?>

Static property access syntax

The general form for reaching a static property:

<?php
ClassName::$statProp;
?>

PHP - More on Static Properties

Static and non-static properties can exist in the same class. A method of that class reaches a static property by writing self and a double colon (::) before the property name:

Example

A method reads a static property of its own class through self:

Create a PHP class called pi with a public static property $value set to 3.14159 and a method staticValue() that returns the static property using the self keyword. Create an instance and echo the result.

> Output: PHP script

Prompt

Create a PHP class called pi with a public static property $value set to 3.14159 and a method staticValue() that returns the static property using the self keyword. Create an instance and echo the result.

Output: PHP script

<?php
class pi {
  public static $value=3.14159;
  public function staticValue() {
    return self::$value;
  }
}

$pi = new pi();
echo $pi->staticValue();
?>

Example

Inside a child class, reach the parent's static property with the parent keyword. The example also reads it directly through the child class name:

Create a PHP class pi with a public static property $value set to 3.14159. Create a child class x that has a method xStatic() returning the parent static property. Echo the value both directly and via the method.

> Output: PHP script

Prompt

Create a PHP class pi with a public static property $value set to 3.14159. Create a child class x that has a method xStatic() returning the parent static property. Echo the value both directly and via the method.

Output: PHP script

<?php
class pi {
  public static $value=3.14159;
}

class x extends pi {
  public function xStatic() {
    return parent::$value;
  }
}

// Get value of static property directly via child class
echo x::$value;

// or get value of static property via xStatic() method
$x = new x();
echo $x->xStatic();
?>