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 . " $METHOD entering");
Sorry, you can't do that. It only works for simple expressions. See here.
Unfortunately there is no way how to do this yet. Example in one of answers here will not work, because {${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}}";
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).
I don’t know the answer to your question, but you can show the class name and method using the __METHOD__ magic constant.
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 )
);
sprintf. –
Persist I've currently settled with string concatenation but it is a pain to type –
Grammar echo sprintf() should never be combined for any reason. If you want to print the formatted string, you simply call printf(). –
Unbated <?php
class test {
public $static = 'text';
public $self = __CLASS__;
// static Method
static function author() {
return "Frank Glück";
}
// static variable
static $url = 'https://www.dozent.net';
public function dothis() {
$self = __CLASS__;
echo <<<TEST
{${!${''}=static::author()}} // works
{$self::author()} // works
{$this->self::author()} // do/don't works but with notice
${!${''}=self::author()} // works
{${$this->self}}::author()}} // do/don't works but with notice
${${self::author()}} // do/don't works but with notice
${@${self::author()}} // works but with @ !
TEST;
}
}
$test = 'test'; // this is the trick, put the Classname into a variable
echo "{$test::author()} {$$test::$url}";
echo <<<HTML
<div>{$test::author()}</div>
<div>{$$test::$url}</div>
HTML;
$test = new test();
$test->dothis();
Output for 8.2.14 - 8.2.17, 8.3.0 - 8.3.4:
Deprecated: Using ${expr} (variable variables) in strings is deprecated, use {${expr}} instead in /in/uGdhi on line 18
Deprecated: Using ${expr} (variable variables) in strings is deprecated, use {${expr}} instead in /in/uGdhi on line 21
Deprecated: Using ${expr} (variable variables) in strings is deprecated, use {${expr}} instead in /in/uGdhi on line 22
Frank Glück https://www.dozent.net<div>Frank Glück</div>
<div>https://www.dozent.net</div>
Warning: Undefined variable $test in /in/uGdhi on line 21
Warning: Undefined variable $Frank Glück in /in/uGdhi on line 22
Frank Glück // works
Frank Glück // works
Frank Glück // do/don't works but with notice
Frank Glück // works
::author()}} // do/don't works but with notice
Frank Glück // do/don't works but with notice
Frank Glück // works but with @ !
Output for 8.1.0 - 8.1.27 (and older)
Frank Glück https://www.dozent.net<div>Frank Glück</div>
<div>https://www.dozent.net</div>
Warning: Undefined variable $test in /in/uGdhi on line 21
Warning: Undefined variable $Frank Glück in /in/uGdhi on line 22
Frank Glück // works
Frank Glück // works
Frank Glück // do/don't works but with notice
Frank Glück // works
::author()}} // do/don't works but with notice
Frank Glück // do/don't works but with notice
Frank Glück // works but with @ !
doesn't work by the way, not don't works. –
Plumate The way I've accomplished it is by setting a variable to the static class itself:
$self = self::class;
Then I can interpolate it:
$string = "This is: {$self::property}";
//define below
function EXPR($v) { return $v; }
$E = EXPR;
//now you can use it in string
echo "hello - three is equal to $E(1+2)";
Just live with the concatenation. You'd be surprised how inefficient variable interpolation in strings can be.
And while this could fall under the umbrella of pre-optimization or micro-optimization, I just don't think you actually gain any elegance in this example.
Personally, if I'm gonna make a tiny optimization of one or the other, and my choices are "faster" and "easier to type" - I'm gonna choose "faster". Because you only type it a few times, but it's probably going to execute thousands of times.
Yes this can be done:
log("{${self::$CLASS}} $METHOD entering");
self::$CLASS as a variable name; so if self::$CLASS == 'foo' then you'll end up with {$foo}, and not 'foo' like you might be expecting. –
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