PHP static variables in double quotes

Question

How can I get PHP to evaluate a static variable in double quotes?

I want to do something like this:

log("self::$CLASS $METHOD entering");

I've tried all sorts of {} combos to get the variable value of self::$CLASS, but nothing has worked. I've currently settled with string concatenation but it is a pain to type:

log(self::$CLASS . " $METHOD entering");

Answer 1

Sorry, you can't do that. It only works for simple expressions. See here.

Answer 2

Unfortunately there is no way how to do this yet. Example in one of answers here will not work, because {${self::$CLASS}} will not returns content of self::$CLASS, but will returns content of variable with name in self::$CLASS.

Here is an example, which does not returns myvar, but aaa:

$myvar = 'aaa';
self::$CLASS = 'myvar';
echo "{${self::$CLASS}}";

Answer 3

I don’t know the answer to your question, but you can show the class name and method using the __METHOD__ magic constant.

Answer 4

Use an anonymous identity function stored in a variable. This way you will have $ immediately after {:

$I = function($v) { return $v; }; $interpolated = "Doing {$I(self::FOO)} with {$I(self::BAR)}";

(I am using class constants in this example but this will work with static variables too).

Answer 5

Just live with the concatenation. You'd be surprised how inefficient variable interpolation in strings can be.

And while this could fall under the umbrella of pre-optimization or micro-optimization, I just don't think you actually gain any elegance in this example.

Personally, if I'm gonna make a tiny optimization of one or the other, and my choices are "faster" and "easier to type" - I'm gonna choose "faster". Because you only type it a few times, but it's probably going to execute thousands of times.

Answer 6

I know this is an old question but I find it odd that noone has suggested the [sprintf][1] function yet.

say:

<?php

class Foo {

    public static $a = 'apple';

}

you would use it with:

echo sprintf( '$a value is %s', Foo::$a );

so on your example its:

log(
    sprintf ( ' %s $METHOD entering', self::$CLASS )
);

Answer 7

Yes this can be done:

log("{${self::$CLASS}} $METHOD entering");