CamelCase comparison, Php

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<?php

// OP version
function FoxJourneyLikeACamelsHump_1(string $string): string {
  $string = preg_replace("/[^[:alpha:][:space:]]/u", ' ', $string);
  $string = ucwords($string);
  $camelCase = preg_replace('/\s+/', '', $string);
  return $camelCase;
}

// Improved version
function FoxJourneyLikeACamelsHumpImproved(string $string): string {
  $string = preg_replace("/[^[:alpha:][:space:]]/u", ' ', $string);
  $string = ucwords($string, ' ');
  $camelCase = str_replace(' ', '', $string);
  return $camelCase;
}

// $expected = "ThQuCkBrWnFXJumpsVRThLZyDG";

$loops = 500000;
$string = " Th3 qu!ck br0wn f0x jumps 0v3r th3 l@zy d0g. ";

$time_start = microtime(true);
for($i=0; $i<$loops; $i++) {
    $is = FoxJourneyLikeACamelsHump_1($string);
}
$time_end = microtime(true);
$tests['Original'] = [$time_end - $time_start, $is];

$time_start = microtime(true);
for($i=0; $i<$loops; $i++) {
    $is = FoxJourneyLikeACamelsHumpImproved($string);
}
$time_end = microtime(true);
$tests['Improved'] = [$time_end - $time_start, $is];

print_r($tests);

[ + ] Show input
Absolute running time: 1.94 sec, cpu time: 1.86 sec, memory peak: 8 Mb, absolute service time: 1,95 sec