strpos: 8.149, substr: 8.816, [0]: 7.388

strpos-vs-substr.php

<?php

$varName = 'test';

$count = 0;
$time = microtime(true);
for ($i = 0; $i < 100000000; $i++) {
     if (0 === strpos($varName . $i, '!')) {
         $count++;
     }
}
$time1 = microtime(true) - $time;

$count = 0;
$time = microtime(true);
for ($i = 0; $i < 100000000; $i++) {
     if ('!' === substr($varName . $i, 0, 1)) {
         $count++;
     }
}
$time2 = microtime(true) - $time;

$count = 0;
$time = microtime(true);
for ($i = 0; $i < 100000000; $i++) {
     if ('!' === ($varName . $i)[0]) {
         $count++;
     }
}
$time3 = microtime(true) - $time;

printf('strpos: %s, substr: %s, [0]: %s', number_format($time1, 3), number_format($time2, 3), number_format($time3, 3));

// strpos: 8.149, substr: 8.816, [0]: 7.388