gistfile1.php

<?php
$counts = 1000000;
$var = "ABCFDSFDSA";

$s1 = time();
for($i = 0; $i < $counts; $i++){
  echo 'XD' . 'XD';
}

$s2 = time();
for($i = 0; $i < $counts; $i++){
    echo "XD" . "XD";
}

$s3 = time();
for($i = 0; $i < $counts; $i++){
    echo 'XD', 'XD';
}

$s4 = time();
for($i = 0; $i < $counts; $i++){
    echo "XD", "XD";
}

$s5 = time();

echo '<br/>';
echo $s2-$s1, "<br/>";
echo $s3-$s2, "<br/>";
echo $s4-$s3, "<br/>";
echo $s5-$s4, "<br/>";
?>