Description:
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I know it has already be discused in #35995.

I do not really agree with that feature (it's accepted by other languages like C, and after assignment it's a variable which is passed to the function), but if this syntax is forbidden then it should make an error, else it is really difficult to fix it in old programs.

Also, because until 5.1.1 it worked like some of us expected, would be nice to add some warning about it in the documentation.

Reproduce code:
---------------
<?php
function myFunc(&$var1) {
    $var1 = 'set in function';
}

$var2 = 'set before function';
myFunc($var2 = 'set in function call');

var_dump($var2);
?>

Expected result:
----------------
Fatal error: Cannot pass parameter 1 by reference in xxxx at line nn

Actual result:
--------------
No error, but the function get in $var1 the assigned value, and after the call $var2 get the assign value too (so not changed by the function)