public function foo($a, $b, $unused, $unused) {
// ... 
}

function foo($x) {
   $x++;
   var_dump(func_get_arg(0));
}
foo(1);

function foo($x) {  
 $x = 42;
 throw new Exception; 
} 
foo("string"); 

$i = 0781; // 8 is not a valid octal digit!
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var_dump(1  -1); // ArithmeticError: Bit shift by negative number

var_dump(1 << 64); // int(0)

var_dump(1  64); // int(0)
var_dump(-1  64); // int(-1)

var_dump("0x123" == "291");   // bool(false)   (previously true) 
var_dump(is_numeric("0x123")); // bool(false)   (previously true) 
var_dump("0xe" + "0x1");    // int(0)     (previously 16) 
var_dump(substr("foo", "0x1")); // string(3) "foo" (previously "oo") 
// Notice: A non well formed numeric value encountered

$str = "0xffff"; 
$int = filter_var($str, FILTER_VALIDATE_INT, FILTER_FLAG_ALLOW_HEX); 
if (false === $int) {   
throw new Exception("Invalid integer!"); 
}
var_dump($int); // int(65535)

$str = "\u{xyz}"; // Fatal error: Invalid UTF-8 codepoint escape sequence

$str = "\\u{xyz}"; // Works fine

$str = "\u202e"; // Works fine

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