The warning "Missing argument X for function()" is reported on the line the function is defined, not the line calling the function. Since a missing argument is an error in the caller, not the callee, the error should be reported at the caller's line number.

Reproducing script:

<?

function NormalFunction($var1, $var2) {
  echo "Normalfunction called with $var1, $var2\n";
}

class ABC {
  function ABC($var1, $var2) {
    echo "I was constructed with $var1, $var2\n";
  }

  function Test($var1, $var2) {
    echo "My test function was called with $var1, $var2\n";
  }
}

NormalFunction(3);                           

$myobj = new ABC(4);

$myobj->Test(5);
?>


<br>
<b>Warning</b>:  Missing argument 2 for normalfunction()
 in <b>/home/david/missingarg.php</b> on line <b>3</b><br>
Normalfunction called with 3, 
<br>
<b>Warning</b>:  Missing argument 2 for abc()
 in <b>/home/david/missingarg.php</b> on line <b>8</b><br>
I was constructed with 4, 
<br>
<b>Warning</b>:  Missing argument 2 for test()
 in <b>/home/david/missingarg.php</b> on line <b>12</b><br>
My test function was called with 5,