


PHP has several commonly used functions for executing system commands, such as: system function, exec function, popen function, passthru, shell_exec function. They can all execute system commands, but the prerequisite is that the system has given permission.
system function
Description: Execute external program and display output data.
Syntax: string system(string command, int [return_var]);
Return value: string
Detailed introduction:
This function is like the function system() in C language, which is used to execute instructions and output the results. If the return_var parameter exists, the status after executing the command will be filled in return_var. It is also worth noting that if you need to process the data entered by the user, but want to prevent the user from playing tricks to crack the system, you can use EscapeShellCmd(). If PHP is executed in a modular fashion, this function will automatically update the output buffer buffer of the web server after each line of output. If you need to return a complete string and don't want to go through unnecessary other intermediate output interfaces, you can use PassThru().
Example code:
The code is as follows | Copy code | ||||
echo "Last line of the output: " . $last_line; echo " Return value: " . $retval; ?> |
exec function
Description: Execute external program.
Return value: string
Detailed introduction:
This function executes the external program or external instruction input command. Its return string is only the last line returned after the external program is executed; if you need a complete return string, you can use the PassThru() function.If the parameter array exists, the command will add the array to the parameter for execution. If you do not want the array to be processed, you can call unset() before executing exec(). If both return_var and array parameters exist, the status after executing the command will be filled in return_var.
代码如下 | 复制代码 |
echo exec("whoami"); |
It is worth noting that if you need to process the data entered by the user and prevent the user from playing tricks to crack the system, you can use EscapeShellCmd().
Example code:
The code is as follows | Copy code |
echo exec("whoami"); ?> |
popen function
Description: Open the file.
代码如下 | 复制代码 |
$fp = popen( "/bin/ls", "r" ); |
The code is as follows | Copy code |
$fp = popen( "/bin/ls", "r" ); ?> |
Use function passthru to execute external system commands
Prototype: function passthru(string $command,int[optional] $return_value)
Knowledge point: The difference between passthru and system. passthru directly outputs the results to the browser without returning any value, and it can output binary, such as image data.
Method 4: Backtick` (in the same key as ~) executes external system commands
The code is as follows
|
Copy code
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||||
echo `dir`; ?>
|

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。

查找方法:1、用strpos(),语法“strpos("字符串值","查找子串")+1”;2、用stripos(),语法“strpos("字符串值","查找子串")+1”。因为字符串是从0开始计数的,因此两个函数获取的位置需要进行加1处理。


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