


PHP obtains memory usage through the built-in function memory_get_usage()
The PHP built-in function memory_get_usage() can return the amount of memory currently allocated to the PHP script, in bytes. . In actual WEB development, these functions are very useful, and we can use them to debug PHP code performance.
The memory_get_usage() function returns the memory usage, the memory_get_peak_usage() function returns the peak memory usage, and getrusage() returns the CUP usage. But please note that these functions need to run on Linux.
Let’s take a look at an example:
The code is as follows:
echo 'Start memory:'.memory_get_usage(), '';
$tmp = str_repeat('hello', 1000);
echo 'Memory after running:'.memory_get_usage(), '';
unset($tmp);
echo 'Return to normal memory:'.memory_get_usage();
Output result:
The code is as follows:
Starting memory: 147296
Memory after running: 152456
Back to normal memory: 147296
In the example, we use str_repeat() to repeat the string "hello" 1000 times, and finally compare the memory consumed before and after. As can be seen from the above example, in order to reduce memory usage, you can use the unset() function to delete variables that are no longer needed. Similar to the mysql_free_result() function, when we no longer need the result set obtained by querying data, we can use it to release the memory occupied by the query.
The function memory_get_usage() can also have a parameter, $real_usage, whose value is a Boolean value. If set to TRUE, obtains the actual memory size allocated by the system. If unset or set to FALSE, emalloc() will report the amount of memory used.
In actual WEB development, you can use PHP memory_get_usage() to compare the memory occupied by each method to choose which method takes up less memory.
The number of bytes returned by the function memory_get_usage() (unit: byte(s)). Here’s a custom function that converts bytes to MB for easier reading:
The code is as follows:
function memory_usage() {
$memory = ( ! function_exists('memory_get_usage')) ? '0' : round(memory_get_usage()/1024/1024, 2).'MB';
Return $memory;
}
Commonly used methods for debugging and testing PHP code performance are:
memory_get_usage can analyze the memory footprint.
You can use the microtime function to analyze program execution time.

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。

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)”。

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。


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