<?php
    $str = "test";
    echo $str."<br>";  //输出test
    echo $str." of php.<br>";  //使用.连接多个字符串，输出test of php.
    echo "test","test1","test2"; //输出用逗号多个参数，输出testtest1test2
?>

<?php
    $str = "admin";
    $number = 123;
    printf("His name is %s,he is %u old.",$str,$number);
    printf("The book is %0.2f$",$number);  //把整型$number按浮点数输出，并保留小数点后两位

    $strs = "He is %1\$s,he has %2\$d children.Their dad is %1\$s,He is %2\$d old.";
    printf($strs,$str,$number);  //按照占位符输出多次变量，%1\$s为第一个参数
?>

<?php
    $str = "admin";
    $txt = sprintf("He is %s",$str);
    echo $txt; //需要的时候使用格式化的$txt
?>