Several commonly used php string functions

<?php
    $a = "@A2345678910JQKA2345678910JQKA2345678910JQKA2345678910JQK@";
    $trim = trim($a,&#39;@&#39;);//去除左右两边的@
    //var_dump($trim);
    $ltrim = ltrim($a,&#39;@&#39;);//去除左边的@
    //var_dump($ltrim);
    $rtrim = rtrim($a,&#39;@&#39;);//去除右边的@
    //var_dump($rtrim);
    $strlen = strlen($a);//统计字符串的长度
    //var_dump($strlen);
    $strrev = strrev($a);//反转字符串
    //var_dump($strrev);
    $str_shuffle = str_shuffle($a);//随机打乱字符串
    //var_dump($str_shuffle);
    $explode = explode(&#39;A&#39;,$a);//以A分割字符串为数组
    //var_dump($explode);
    $implode = implode(&#39;A&#39;,$explode);//把$explode这个数组使用A拼接为字符串
    //var_dump($implode);
    $str_replace = str_replace(&#39;A&#39;,&#39;B&#39;,$a);//字符串替换 把$a字符串中的A替换为B
    //var_dump($str_replace);
    $strpos = strpos($a,&#39;Q&#39;);//查找Q在$a中首次出现的位置
    //var_dump($strpos);
    $strrpos = strrpos($a,&#39;Q&#39;);//查找Q在$a中最后一次出现的位置
    //var_dump($strrpos);
    $b = &#39;i love you&#39;;
    $strtoupper = strtoupper($b);//字符串转换为大写
    //var_dump($strtoupper);
    $c = &#39;I LOVE YOU&#39;;
    $strtolower = strtolower($c);//字符串转换为小写
    //var_dump($strtolower);
    $ucwords = ucwords($b);//字符串每个单词的首字母大写
    //var_dump($ucwords);
    $ucfirst = ucfirst($b);//字符串首字母的写
    //var_dump($ucfirst);
    $substr = substr($a,&#39;-1&#39;);//字符串截取从倒数第一个开始截取
    //var_dump($substr);
    $strstr = strstr($a,&#39;Q&#39;);//查找字符串$a中Q首次出现的位置并返回这个位置到结束的字符串
    //var_dump($strstr);
    $strrchr = strrchr($a,&#39;Q&#39;);//查找Q在字符串最后一次出现的位置返回从这个位置到结尾的字符串
    //var_dump($strrchr);
    $str_repeat = str_repeat($a,&#39;2&#39;);//重复$a这个字符串2次以后的结果
    //var_dump($str_repeat);
 
?>

The above has introduced several commonly used PHP string functions, including related content. I hope it will be helpful to friends who are interested in PHP tutorials.