Simulated Ruby symbols in PHP -

ruby , other languages have convenient feature: symbols. in-place constants. wonder if following approach simulating symbols in php an @ sign before unquoted string valid approach.

$array = [@key => "value"]; echo sprintf("%s php symbols %s\n", @testing, $array[@key]); 

i understand there drawbacks against formal constants , like, same ruby's symbols: consider typing errors. there other considerations against using approach?

you suppressing error (a notice, exact). not costs processing time mentioned in cwallenpoole's answer, error there reason. reason is:

notice: use of undefined constant hello - assumed 'hello' in ... 

you relying on constant being undefined - notice trying tell you. if constant of name defined, grab value instead.

in ruby, :__line__ quite different __line__. former symbol - equals no matter use it. latter number, , magical variable changes value on every line. in php, @__line__ same __line__, because there no error suppress. oh, , there's 1 special "symbol" extra-fun debug: @exit, aka @die.

in ruby, can use sorts of symbols including operators , keywords. these (and many more) valid: :+ :* :< :<< :[] :[]= :while :case :x=. pair of parentheses, can use symbols :case= , :while=. in php, none of these work. you'll end parse error. won't suppressed. exception @[] in php 5.4, produces empty array. on other hand, lots of php expressions not valid ruby symbols: @(1+1) === @2 @1 == @'1'

ruby's symbols not equal else. purpose of existence. sure, have nice properites to_s , to_proc, original purpose serve identifiers separate possible user input. sorta nice example if using symbols represent tokens in lexer stream, such [:lparen, 1, :plus, "rparen", :rparen]. in php, undefined constants strings. in ruby, ?test != "test". in php @test === "test" (assuming dindn't define constant named "test" equal else).

you can't assume non-magic constants won't change. can't attribute malice can explained bad coding. nothing of worry in ruby:

//in library code: $this->status = @done; // bad  //outside library code: define('done', "no"); // bad define(@done, "yes"); // worse echo @no; // prints "yes"  //in library code: if($this->status == @done){   //won't execute }  echo @die; echo "this won't printed!"; 

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you shouldn't rely on constants being undefined, , shouldn't use error suppressing hide error messages telling that. shouldn't use special notation pretend 2 things not equal when are. also, can trust users of library not redefine constants @ runtime?