How to define and declare a variable by calling a function in a php class

Question

I'm used to set and declare my parameters in a php function like this:

function foo( $length = 24 ) { ...

Now I would like to do that with a class-function:

class foo{   
    function configuration() {
      $this->defaultLength = 24;
    }
    function foo() {
      $this->configuration();
    }
    function test($length = $this->defaultLength) {...

by calling:

$r = new foo();
$r->test();

I get this error message: Parse error: syntax error, unexpected '$this' (T_VARIABLE) in /www/htdo..

How can I define and declare a variable in a php class?

Federkun · Accepted Answer · 2016-03-03 16:25:15Z

2

I would do this:

class foo
{   
    const DEFAULT_LENGHT = 24;

    public function test($length = self::DEFAULT_LENGHT)
    {
        var_dump($length);    
    }
}

$foo = new foo();
$foo->test(); // // int(24)

If you need to change that value in runtime, you can do something like this:

class foo
{   
    protected $default_lenght = 24;

    public function setDefaultLenght($lenght)
    {
       $this->default_lenght = $lenght;
    }

    public function test($length = null)
    {
        $length = $length ?: $this->default_lenght;
        var_dump($length);
    }
}

$foo = new foo();
$foo->test(); // int(24)
$foo->setDefaultLenght(42);
$foo->test(); // int(42)

edited Mar 3, 2016 at 16:25

answered Mar 3, 2016 at 16:15

Federkun

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3 Comments

Federkun Over a year ago

@E_p, my bad, sorry I was distracted

E_p Over a year ago

NP add public before test function and code review passed :).

Federkun Over a year ago

This really hasn't been my day, I swear that I always follow PSR-2 specification :P

Davis · Accepted Answer · 2016-03-03 16:26:10Z

1

You can't reference $this in your function signature. You could do something like:

public function test ($length = null) {
    if ($length === null) {
        $length = $this->defaultLength;
    }
}

edited Mar 3, 2016 at 16:26

answered Mar 3, 2016 at 16:11

Davis

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2 Comments

Jaquarh Over a year ago

Why can't he? if he wants to use it as $r->test(); then $this->defaultLength is accessible if he declares it in the same Scope (inside the class).

Erik Over a year ago

Inside the function, yes. But not inside the function signature, since the function signature is read before any instance is created.

Unex · Accepted Answer · 2016-03-03 16:43:19Z

You could build an array with the element of the signature of your function, filter them and merge it with a default configuration calling all the functions you need. I made a simple example with defining 2 parameter with different functions.

class foo{   

    private $configuration;

    private function buildDefaultConfiguration() {
        return $configuration = array(
            'defaultLength' => $this->getDefaultLength(),
            'defaultWidth'  => $this->getDefaultWidth(),
        );
    }

    public function __construct($givenLength = null, $givenWidth = null) {
        $givenConfiguration = array(
            'defaultLength' => $givenLength,
            'defaultWidth'  => $givenWidth
        );
        $givenConfiguration = array_filter($givenConfiguration);
        $defaultConfiguration = $this->buildDefaultConfiguration();
        $this->configuration = array_merge($defaultConfiguration, $givenConfiguration);
    }

    public function test()
    {
        echo $this->configuration['defaultLength'] . ' - ' . $this->configuration['defaultWidth'];
    }

    private function getDefaultLength()
    {
        return 24;
    }

    private function getDefaultWidth()
    {
        return 12;
    }
}

$foo1 = new foo(13,14);
$foo2 = new foo();
$foo3 = new foo(null, 66);
$foo4 = new foo(66);

$foo1->test();
//result is 13 - 14
$foo2->test();
//result is 24 - 12
$foo3->test();
//result is 24 - 66
$foo4->test();
//result is 66 - 12

You can check a live working example here, formatting isn't great though Hope this'll help you

Big Zak · Accepted Answer · 2016-03-03 16:23:58Z

0

class foo{  
//set the default lenght first 
var $defaultLength = 0;

function configuration() {
  $this->defaultLength = 24;
}


function setLength($newLength){
 $this->defaultLength = $newLength;
}

function test($length = null) {
 //if length is null assign default
 if($length == null){
$length = $this->defaultLength; 
 }

}

$foo = new foo();
$this->configuration();
$foo->test(); // int(24)
$foo->setLength(42);
$foo->test(); // int(42)

answered Mar 3, 2016 at 16:23

Big Zak

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