实例演示字符串函数

md5(),把字符串进行md5加密

//md5()两个参数
//1.要计算的字符串
//2.可选,true,md5返回16字符长度的2进制,默认false,返回32字符的16进制数
echo md5('你好545'), '<br>';
echo md5('你好545', true);

quotemeta(),转义元字符集,给字符串特特殊字符添加转义符

$str = "Hello world. (can you hear me?)";
echo quotemeta($str);
//返回 Hello world\. \(can you hear me\?\)

str_shuffle(),随机打乱字符串

$shuffled = str_shuffle('abcdef');
echo $shuffled;

strrev(),反转字符串

echo strrev("Hello world!");

substr_count(),计算字符串出现次数

$text = 'This is a test';
echo substr_count($text, 's'); // 3
echo substr_count($text, 's', 5); // 2,从第6个开始计算,只有两个s

ucfirst(),将字符串首字母转换成大写

$foo = ucfirst('hello world!');
echo $foo;