PHP concatenation test

Dot: $a.$a
2.3812799453735
Curly braces: {$a}{$a}
2.4255859851837
Comma: $a,$a
3.1888210773468

Note: The test is based on 10 million concatenations for each case, so that after each subtest the output buffer is cleaned (PHP7). The result shows that concatenation with curly braces is ≈3% slower than dot concatenation. Concatenation with comma is the slowest, being ≈33% slower than dot concatenation. The results may vary.