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<?php // define( // 'FOO_CONSTANT', // array( // 'link' => array( ':hover', ':focus', ':active' ), // ) // ); // var_dump( array_key_exists( 'link', FOO_CONSTANT ) ); // var_dump( isset( FOO_CONSTANT['link'] ) ); class Foo { const VALID_ELEMENT_PSEUDO_SELECTORS = array( 'link' => array( ':hover', ':focus', ':active' ), ); } // Works.in >= PHP 5.6. var_dump( array_key_exists( 'link', FOO::VALID_ELEMENT_PSEUDO_SELECTORS ) ); var_dump( ! empty( FOO::VALID_ELEMENT_PSEUDO_SELECTORS['link'] ) ); // Doesn't work on < PHP 7.0. var_dump( isset( FOO::VALID_ELEMENT_PSEUDO_SELECTORS['link'] ) );
Output for 8.1.23 - 8.1.34, 8.2.10 - 8.2.31, 8.3.0 - 8.3.31, 8.4.1 - 8.4.22, 8.5.0 - 8.5.7
bool(true) bool(true) bool(true)
Output for 5.6.40
Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead) in /in/lrFo3 on line 23
Process exited with code 255.

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