echo $myvar1;
echo 1,2,$myvar,"<b>bold</b>";

int print ( string arg )
Outputs arg . Returns 1 , always.

int printf ( string format [, mixed args [, mixed ...]] )// Produces output according to format , which is described in the documentation for sprintf() .// Returns the length of the outputted string. 

$name = "hunte";
$age  = 25;
printf("my name is %s, age %d", $name, $age);

string sprintf ( string format [, mixed args [, mixed ...]] )// Returns a string produced according to the formatting string format .

printf()函数的调用格式为:
printf("<格式化字符串>", <参量表>);%d  十进制有符号整数
%u  十进制无符号整数
%f  浮点数
%s  字符串
%c  单个字符
%p  指针的值
%e  指数形式的浮点数
%x, %X 无符号以十六进制表示的整数
%o  无符号以八进制表示的整数
%g  自动选择合适的表示法

   ①\n     换行 ②\f     清屏并换页 ③\r     回车 ④\t     Tab符 ⑤\xhh   表示一个ASCII码用16进表示, ⑥其中hh是1到2个16进制数

$n =  43951789;
$u = -43951789;
$c = 65; // ASCII 65 is 'A'
// notice the double %%, this prints a literal '%' character
printf("%%b = '%b'\n", $n); // binary representation
printf("%%c = '%c'\n", $c); // print the ascii character, same as chr() function
printf("%%d = '%d'\n", $n); // standard integer representation
printf("%%e = '%e'\n", $n); // scientific notation
printf("%%u = '%u'\n", $n); // unsigned integer representation of a positive integer
printf("%%u = '%u'\n", $u); // unsigned integer representation of a negative integer
printf("%%f = '%f'\n", $n); // floating point representation
printf("%%o = '%o'\n", $n); // octal representation
printf("%%s = '%s'\n", $n); // string representation
printf("%%x = '%x'\n", $n); // hexadecimal representation (lower-case)
printf("%%X = '%X'\n", $n); // hexadecimal representation (upper-case) printf("%%+d = '%+d'\n", $n); // sign specifier on a positive integer
printf("%%+d = '%+d'\n", $u); // sign specifier on a negative integer
The printout of this program would be:
%b = '10100111101010011010101101'
%c = 'A'
%d = '43951789'
%e = '4.39518e+7'
%u = '43951789'
%u = '4251015507'
%f = '43951789.000000'
%o = '247523255'
%s = '43951789'
%x = '29ea6ad'
%X = '29EA6AD'
%+d = '+43951789'
%+d = '-43951789'

$s = 'monkey';
$t = 'many monkeys'; printf("[%s]\n",      $s); // standard string output
printf("[%10s]\n",    $s); // right-justification with spaces
printf("[%-10s]\n",   $s); // left-justification with spaces
printf("[%010s]\n",   $s); // zero-padding works on strings too
printf("[%'#10s]\n",  $s); // use the custom padding character '#'
printf("[%10.10s]\n", $t); // left-justification but with a cutoff of 10 characters
  The printout of this program would be:
[monkey]
[    monkey]
[monkey    ]
[0000monkey]
[####monkey]
[many monke]

$isodate = sprintf("%04d-%02d-%02d", $year, $month, $day);

$money1 = 68.75;
$money2 = 54.35;
$money = $money1 + $money2;
// echo $money will output "123.1";
$formatted = sprintf("%01.2f", $money);
// echo $formatted will output "123.10" 

$number = 362525200;
echo sprintf("%.3e", $number); // outputs 3.63e+8