What does it do

Question

$ top + = $ i? 12-0;

Answer 1

If $i is

• set
• not false
• not null

increment $top by twelve; otherwise, by zero, implicitly turning $top ( not $i ) into a numerical variable if it is not already one.

Answer 2

If $i has the value set (a non-empty / empty value means that the condition resolves to true), then 12 is added to $top and 0 otherwise.

This is basically a reduction:

 if ($i) { $top += 12; } else { $top += 0; } 

This is called the Ternary statement.

Answer 3

Abbreviation for:

 if ($i) { $top += 12; } 

Answer 4

If $ i is true (for example, not zero or an empty string), then 12 is added to $ top. Otherwise, nothing is added to $ top.

It is equivalent

 if($i) $top = top + 12; 

Answer 5

Increase the value of $top by 12 if $i has a true Boolean value (i.e. $i = 1 , $i = true , etc.) or 0 if not.

http://www.php.net/manual/en/language.operators.assignment.php

Ternary operator

Answer 6

http://en.wikipedia.org/wiki/Ternary_operation

Answer 7

$ i? 12-0 is the expression for “transcripts”. In this case, $ i is evaluated as an expression. If the expression is true, then 12 is used as the r-value in the addition assignment expression. If $ i evaluates to false, then 0 is used as the r-value.