How to flip a string in php

php flips strings, a test point that often appears in some interview questions. Flip strings in PHP come with the strrev() function. You can also use a for loop with mb_substr() or str_split() to achieve the same function without using PHP's built-in functions.

##1. strrev() flips the string (Recommended learning: PHP Programming From entry to master)

<?php 
$str = &#39;Hello World!&#39;; 
echo strrev($str);

2. for mb_substr() flips the string

The number and position of the for loop, each time mb_substr goes from the end to characters and the process of splicing them together

<?php 
$newstr = &#39;&#39;; 
$str = &#39;Hello World!&#39;;
for($i=1;$i<=strlen($str);$i++){     
    $newstr.=mb_substr($str,-$i,1); 
} 
echo $newstr;
 
#换种方式
$newstr = &#39;&#39;;
$str = &#39;Hello World!&#39;;
for($i=strlen($str);$i>=1;$i--){
    $newstr.=mb_substr($str,$i-1,1);
}
echo $newstr;

3. for str_split() flips the string

str_split() function puts each character of the string into into the array, the for loop traverses the array keys, and the process of splicing the values

<?php 
$newstr = &#39;&#39;; 
$str = &#39;Hello World!&#39;; 
$str_arr = str_split($str); 
for($i=count($str_arr)-1;$i>=0;$i--){     
    $newstr.=$str[$i]; 
} 
echo $newstr

These three methods can eventually flip the string and output the result: !dlroW olleH

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