PHP: use default value when calling a function.

Question

in PHP you can call a function. by not calling all parameters by using these statement.

function test($t1 ='test1',$t2 ='test2',$t3 ='test3')
{
echo "$t1, $t2, $t3";
}

and you can just use the function like this

test();

lets just say I want the last one to be different but not the others. the only way i know is by doing this with no succes

test('test1','test2','hi i am different');

is there a other way for doing this I tried this.

test(,,'hi i am different');
test(default,default,'hi i am different');

thanks matthy

Answer 1

The parameters with default values have to be last, after the others, in PHP and all the others up to that point must be filled in when calling the function. I don't know of anyway to pass a value that triggers the default value.

Answer 2

Use arrays :

function test($options = array()) {
    $defaults = array(
        't1' => 'test1',
        't2' => 'test2',
        't3' => 'test3',
    );
    $options = array_merge($defauts, $options);
    extract($options);
    echo "$t1, $t2, $t3";
}

Call your function this way :

test(array('t3' => 'hi, i am different'));

Answer 3

What I normally do in those situations is to specify the parameters as an array instead. Have a look at the following example (untested):

<?php
test(array('t3' => 'something'));

function test($options = array())
{
  $default_options = array('t1' => 'test1', 't2' => 'test2', 't3' => 'test3');
  $options = array_merge($default_options, $options);

  echo $options['t1'] . ', ' . $options['t2'] . ', ' . $options['t3'];
}
?>

Answer 4

You can't do that using raw PHP. You can try something like:

function test($var1 = null, $var2 = null){
    if($var1 == null) $var1 = 'default1';
    if($var2 == null) $var2 = 'default2';
}

and then call your function, with null as the identifier of the default variable. You can also use an array with the default values, that will be easier with a bigger parameter list.

Even better is to try to avoid this all, and rethink your design a bit.