Check if string is palindrome (case insensitive)

isPalindrome.php

<?php
// Complexity: O(n/2)
function isPalindrome($str) {
	$array = str_split($str);
	$arrayLen = sizeof($array) - 1;
	foreach ($array as $index => $currChar) {
		$indexFromBehind = $arrayLen - $index;
		$charFromBehind = $array[$indexFromBehind];
		$charFromBehindLowerCase = strtolower($charFromBehind);
		$currCharLowserCase = strtolower($currChar);
	 	if ($currCharLowserCase !== $charFromBehindLowerCase) return false;
	 	$pivotIndex = $arrayLen / 2;
	 	$reachedPivotIndex = $index === $arrayLen / 2;
	 	if ($reachedPivotIndex) break;
	}
	return true;
}

var_dump(isPalindrome('dad'));
var_dump(isPalindrome('mom'));
var_dump(isPalindrome('ohhohho'));
var_dump(isPalindrome('ohhohhO'));
var_dump(isPalindrome('ohhohhOk'));
var_dump(isPalindrome('Deleveled'));