/*************by garcon1986*********/
//print和echo的区别:
//1. echo可以输入多个字符串,而print不能。
print "hello"."world"; //成功
echo "hello"."world"; //成功
//print "hello","world"; //失败
echo "hello","world"; //成功
//2. echo比print更快。
$stime = microtime(true);
print "hello"."world";
$etime = microtime(true);
$total = $etime - $stime;
echo $total.'
';
//microtime — Return current Unix timestamp with microseconds
$stime2 = microtime(true);
echo "hello"."world";
$etime2 = microtime(true);
$total2 = $etime2 - $stime2;
echo $total2.'
';
//执行结果:
//helloworld0.0014331340789795
//helloworld0.00018310546875
//看到echo比print更快。
//print_r — Prints human-readable information about a variable 或数组
$a = "sajfd sfjal sfjalwureoi weu sj we fk io ";
print_r($a);
echo '
';
$a = array("b","c","d");
print_r($a);
echo '
';
//var_dump — Dumps information about a variable 或数组
//var_dump -- 打印变量的相关信息
$a = "sajfd sfjal sfjalwureoi weu sj we fk io ";
var_dump($a);
echo '
';
$a = array("b","c","d");
var_dump($a);
echo '
';
var_dump(array("b","c","d"));
echo '
';
?>
/************by garcon1986********/
//%% - 返回百分比符号
//%b - 二进制数
//%c - 依照 ASCII 值的字符
//%d - 带符号十进制数
//%e - 可续计数法(比如 1.5e+3)
//%f - 浮点数(local settings aware)
//%F - 浮点数(not local settings aware)
//%o - 八进制数
//%s - 字符串
//%u - 无符号十进制数
//%x - 十六进制数(小写字母)
//%X - 十六进制数(大写字母)
//printf()函数输出格式化的字符串
$str = "hello";
$number = 456;
//example1
printf("%s world. Day number %s", $str, $number); //输出: hello world. Day number 456
print "
";
//example2
printf("%%", $number); //%
print "
";
printf("%b", $number); //111001000
print "
";
printf("%c", $number); //ascii码
print "
";
printf("%d", $number); //456
print "
";
printf("%e", $number); //4.560000e+2
print "
";
printf("%f", $number); //456.000000
print "
";
printf("%F", $number); //456.000000
print "
";
printf("%o", $number); //710
print "
";
printf("%s", $number); //456
print "
";
printf("%u", $number); //456
print "
";
printf("%x", $number); //1c8
print "
";
printf("%X", $number); //1C8
print "
";
printf("With 2 decimals: %1\$.2f
With no decimals: %1\$u
",$number);
//With 2 decimals: 456.00
//With no decimals: 456
printf("With 2 decimals: %f
With no decimals: %1\$u
",$number);
//With 2 decimals: 456.000000
//With no decimals: 456
//fprintf() 函数把格式化的字符串写到指定的输出流(例如:文件或数据库)。
$file = fopen("text.txt","w");
echo fprintf($file, "fprintf 1: %s world. Day number %u", $str, $number).'
'; //38
echo fprintf($file, "fprintf 2: %f", $number).'
'; //21
echo fprintf($file,"fprintf 3: With 2 decimals: %1\$.2f\nWith no decimals: %1\$u",$number).'
'; //56
//vprintf()函数输出格式化的字符串。
//vprintf() 中的 arg 参数位于数组中。数组的元素会被插入主字符串的百分比 (%) 符号处。该函数是逐步执行的。在第一个 % 符号中,插入 arg1,在第二个 % 符号处,插入 arg2,依此类推。
vprintf("vprintf: %s world. Day number %u", array($str,$number)); //vprintf: hello world. Day number 456
echo '
';
//sprintf() 函数把格式化的字符串写写入一个变量中。
$txt = sprintf("sprintf: %s world. Day number %u",$str,$number);
echo $txt.'
'; //sprintf: hello world. Day number 456
//vfprintf() Operates as fprintf() but accepts an array of arguments, rather than a variable number of arguments.
echo vfprintf($file, "vfprintf: %s world! Day number %u", array($str, $number)).'
'; //37
//vsprintf() Operates as sprintf() but accepts an array of arguments, rather than a variable number of arguments.
$txt = vsprintf("vsprintf: %s world. Day number %u",array($str,$number));
echo $txt.'
'; //vsprintf: hello world. Day number 456
?>

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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