php如何实现字符串翻转

print_r(strrev($str));

$newArrOne = [];//初始化一个新的数组
$newStrOne = '';//初始化一个新的字符串
$newArrOne = str_split($str);
$arrCount = count($newArrOne);
for ($i=0; $i < $arrCount; $i++) {
$newStrOne.=$newArrOne[$i];
}
echo "<pre class="brush:php;toolbar:false">";
print_r($newStrOne);
echo "

$newStrTwo = '';//初始化一个新的字符串
$arrCountTwo = strlen($str);
for ($i=1; $i <= $arrCountTwo; $i++) {
$newStrTwo.=substr($str, -$i, 1);
}
echo "<pre class="brush:php;toolbar:false">";
print_r($newStrTwo)."\n";
echo "

$newStrThree = '';//初始化一个新的字符串
$arrCountThree = strlen($str);
for ($i = $arrCountThree; $i>=0;$i--) {
@$newStrThree.=$str[$i];
}
echo "<pre class="brush:php;toolbar:false">";
print_r($newStrThree)."\n";
echo "