Instructions for using ternary operators in PHP

Today, a netizen in the group sent a topic not difficult, but may be wrong
Copy Code code as follows:
Echo
$a = = 1? ' One ':
$a = = 2? ' Two ':
$a = = 3? ' Three ':
$a = = 4? ' Foura ': ' Other ';
echo "\ n";

The output results are:

<BR>

The result: four

At first I don't understand, according to my understanding, should be such logic:
echo ($a = 1? ' One ':
($a = = 2? ' Two ':
($a = = 3? ' Three ':
($a = = 4? ' Four ': ' Other '));
Output is: two

Later in Keving (qq:48474), see the PHP manual, finally understand the PHP ternary character interpretation is from left to right,
<!--? php
At first glance the output below is ' true '
Echo (true? ') True ': false? ' T ': ' F ');

However, the actual output of the above statement is ' t ' because the ternary operator is computed from left to right.

Here is the equivalent of the statement above, but more clearly
Echo (true? ' True ': ' false '? ' t ': ' F ');

So the above can be explained as follows:
Echo (
(($a = = 1?) ' One ':
$a = = 2)? ' Two ':
$a = = 3)? ' Three ':
$a = = 4)? ' Four ': ' Other ');

In fact, this involves type conversions:
$a ==1=>false=> $a ==2?true=> ' two ' =true=> ' three ' =true=> ' four '