先思考一个问题:
如下代码会向页面显示什么?
代码如下 | |
|
|
代码如下 | |
die(123); ?> |
die(123);
?>
曾经有段时间我一直认为 页面会显示 123,但实践结果告诉我,答案错了,页面一片空白!
代码如下 | |
echo '123'; die(); ?> |
代码如下 | |
echo '123'; die(); ?> |
A piece of information on the Internet:
The difference between exit() and die() in PHP
PHP manual: die()Equivalent to exit().
Note: die() and exit() are both functions to terminate script execution; in fact, the two names exit and die point to the same function, and die() is an alias of the exit() function. This function only accepts one parameter, which can be a value returned by a program or a string, or no parameters can be entered, and the result is no return value.
Reference: Although the two are the same, there are subtle selectivity in their usual use. For example:
When the value passed to the exit and die functions is 0, it means that the execution of the script is terminated early, usually with the name exit().
The code is as follows | |||||
echo "1111";
exit(0);
echo "2222"; |
// 22222 will not be output because when the program reaches exit(0), the script has been terminated early and "will die immediately".
代码如下 | |
$fp=fopen("./readme.txt","r") or die("不能打开该文件"); |
2 // In this case, if the fopen function is called and returns a Boolean value of false, die() will immediately terminate the script and print
immediately3 // The string passed to it, "I can say one or two words before I die".
------------------------------------------------ ----------------------------------
Returning to the previous topic, why doesn’t the following code output 123 to the page?
The code is as follows | |
|
|
代码如下 | |
die(123); // 或 exit(123); ?> |
die(123);
// or exit(123);
?>
Summary by yourself:
1. Functionally, die() is equivalent to exit();
2. PHP has multiple running modes, either in website form or in script form (no Web server is required).
When PHP is run in script form, it is recommended to use exit():
For example, the Bash Shell script language, when it wants to stop running, will use the exit() function to terminate the script and allow the output content to the running environment (usually stored in a global variable), but the output content is only Can be a number, indicating the "end status of the command".
In other words, exit(123) only outputs a running status of 123, rather than actually outputting 123 to the console. If you want to output 123 to the console, the code must be changed to the following form:
The code is as follows | |
|
|
代码如下 | |
exit('123'); |
exit('123');
?>
When PHP is running as a website, it is recommended to use die():
But at this time, die (number) is meaningless, because it will not output a number string to the page. In other words, if you want the page to terminate and output numbers, you have to change it to the following form
代码如下 | |
die('123'); ?> |
The code is as follows | |
die('123'); ?> |

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。

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。

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。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。


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