passing variable names as string

Question

I'm trying to perform the same function dosomething() to multiple variables $lastsum $avatar $angels $city $square in PHP.

$lastsum->dosomething();
$avatar->dosomething();
$angels->dosomething();
$city->dosomething();
$square->dosomething();

Is there a way to make this code cleaner by listing the names of the variables in a string array and perform the function with a for loop. I'm looking for something like this. Does anyone know the right way to do this in PHP?

$all = ['lastsum' , 'avatar', 'angels' , 'city' , 'square'];
foreach (....){
    $(nameofvariable)->dosomething();
}

user187291 · Accepted Answer · 2010-11-25 20:53:40Z

4

What's wrong with

$all = array($lastsum , $avatar, $angels, $city, $square);
foreach (....){
    $variable->dosomething();
}

To achieve exactly what you're looking for, use variable variables

$all = array('lastsum' , 'avatar', 'angels' , 'city' , 'square');
foreach ($all as $x) {
    $$x->dosomething();
}

Many people consider this to be bad style though.

answered Nov 25, 2010 at 20:53

user187291

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Comments

Alan Haggai Alavi · Accepted Answer · 2010-11-25 20:48:12Z

1

Not an elegant solution. However, you could make use of eval():

$all = array( 'lastsum' , 'avatar', 'angels', 'city', 'square' );

foreach ( $all as $var ) {
    $code = "\$${var}->dosomething();";
    eval($code);
}

Otherwise, store the objects in an array:

$all = array( $lastsum , $avatar, $angels, $city, $square );

foreach ( $all as $obj ) {
    $obj->dosomething();
}

answered Nov 25, 2010 at 20:48

Alan Haggai Alavi

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2 Comments

user419017 Over a year ago

I must ask - why eval? Why don't you just execute the $code right there?

Alan Haggai Alavi Over a year ago

netcoder and Zenph: Oh! I was not aware of that. Thank you for pointing it out.

netcoder · Accepted Answer · 2010-11-25 20:54:31Z

1

If you want to use variables variables, it would be more like this:

function dosomething(&$var) {
   $var .= 'bar';
}

$a = 'foo';
$b = 'bar';
$vars = array('a', 'b');
foreach ($vars as $var) {
   dosomething($$var); 
}

var_dump($a); // foobar
var_dump($b); // barbar

If $a is an object, then you can do $$var->dosomething().

EDIT: NOTE: In most cases, if you have to use variables variables, you may want to consider using a proper data structure instead, like an array.

edited Nov 25, 2010 at 20:54

answered Nov 25, 2010 at 20:39

netcoder

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1 Comment

netcoder Over a year ago

@Mark: Heh. I have yet to find a use for variables variables. I think is was carried over from the register_globals era or something. Because an array provide similar functionality and a lot more.

Marc B · Accepted Answer · 2010-11-26 03:04:33Z

1

Another alternative:

$all = array('lastsum' , 'avatar', 'angels' , 'city' , 'square');

foreach ($all as $x) {
   $GLOBALS[$x]->dosomething();
}

Not sure if you could do method calls from the GLOBALS superglobal, but you could most likely access static properties/functions.

answered Nov 26, 2010 at 3:04

Marc B

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