echo-comma vs. echo-period vs. echo-double-quotes vs. echo-echo
Echo can be used to output concatenated variables in an interesting way. Unlike Print, you can concatenate strings with a comma instead of a period. But is it really all that much better than the old fashioned concatenation with a period, or embedding your variables within double-quotes?
For this test, I'm using the loopTest.php gist with the following parameters:
$testString = generateRandomString(500);
// example:
loopTime(0.5 /* seconds to run per function */,
   function(){
       global $testString;
       echo 'test ', $testString;
   },
   function(){
       global $testString;
       echo 'test ' . $testString;
   },
   function(){
       global $testString;
       echo 'test ';
       echo $testString;
   },
   function(){
       global $testString;
       echo "test $testString";
   }
);
Results (larger is better):
 1)   389,648 iterations in 0.50 seconds.
 2)   365,994 iterations in 0.50 seconds.
 3)   383,308 iterations in 0.50 seconds.
 4)   351,916 iterations in 0.50 seconds.
Echo with a comma or two echo calls are equally fast
Using a period to concatenate strings for echo is the slow.
Embedding the variable within double-quotes is slowest.
