Programmer-Add a php udf to the front & why is the effect the same? All the code above

$ A & #039; wap & #039; $ B & #039; kkk & #039; {code...} $ a = 'wap ';
$ B = 'kkk ';

Function sum ($ p) {return $ p. = 'aaa';} function & sum2 ($ p) {return $ p. = 'bbb ';} echo sum ($ a); echo"
"; Echo sum2 ($ B );

Reply content:

$ A = 'wap ';
$ B = 'kkk ';

Function sum ($ p) {return $ p. = 'aaa';} function & sum2 ($ p) {return $ p. = 'bbb ';} echo sum ($ a); echo"
"; Echo sum2 ($ B );

I have answered your related questions in another question. In this example, if you want to compare them, you can change the code:

$ A = 'wap '; $ B = 'kkk'; function sum ($ p) {return $ p. = 'aaa';} function & sum2 (& $ p) {return $ p. = 'bbb ';} // since the reference is returned, it cannot be passed using the form parameter, so change $ p to & $ p echo sum ($ ); // output is wapaaa echo"
"; Echo sum2 ($ B); // output is kkkkbbb echo"
"; Echo sum ($ a); // output is wapaaa echo"
"; Echo sum2 ($ B); // output is kkkkbbbbbb