致命错误php-意外'）'

Question

this code gives me the error :

FATAL ERROR syntax error, unexpected ')', expecting '(' on line number 10 -- line 10 is this one: "if ( ! empty( EMPTY ) ) { "

I don't get it...could you help explaining?

define('CONSTANT', 1);

define('_CONSTANT', 0);

define('EMPTY','');

if  ( ! empty( EMPTY ) ) {

    if ( ! ( ( boolean ) _CONSTANT ) ) {

        print "One";

    }

} else if ( constant( 'CONSTANT' == 1 )) {

    print "TWO";

}

Answer 1

In PHP method names are case-insensitive. For example, these statements are doing the same thing:

echo empty(0);
//out: 1
echo emPTY(0);
//out: 1
echo EMPTY(0);
//out: 1

You are trying to define a constant that has the same name as built-in PHP method empty . When you call empty(EMPTY) (which is the same as empty(empty) PHP thinks that you are trying to call (outer) empty on result of (inner) EMPTY invocation, but oops, your inner EMPTY is not a method invocation at all (it misses the braces). During building AST PHP expects something like empty(EMPTY(...)) (note the open brace after inner EMPTY ) and that's why you are getting syntax error expecting "("... .

Answer 2

Use defined because empty check variables and you are checking on constants. defined — Checks whether a given named constant exists. As its said here defined Documentation