PHP Concatenation – Comma (,) vs Dot (.)

While on a chat with a friend who recently started learning PHP programming language, he ask me what is the difference between using a comma (,) and a dot (.) as a concatenator.

My answer to him was: for the record, comma isn’t a concatenator. it use for printing or rather echoing a list of variable, string and numbers similar to how it is used in English. While dot joins two strings together to make one longer string.

Take note: comma only work when using the echo language construct and you can’t return a comma delimited variable.

Examples

Let’s see some code example.

• 
  <?php
  $a = 'i am';
  $b = ' boy';
  echo $a, $b;
  

  
  <?php
  $a = 'i am';
  $b = ' boy';
  $c = $a . $b;
  echo $c;
  

  
  <?php
  $a = 'i am';
  $b = ' boy';
  echo $a . $b;
  

  Result: i am boy

• 
  <?php
  $a = 'i am';
  $b = ' boy';
  print($a, $b);
  

  
  <?php
  $a = 'i am';
  $b = ' boy';
  $c = $a, $b;
  

  
  <?php
  $a = 'i am';
  $b = ' boy';
  return $a , $b;
  

  Result: Parse error: syntax error, unexpected ‘,’ in C:\xampp\htdocs\index.php on line 4

It is worth noting that when using echo, delimiting string with comma is faster than dot.