新手问个很简单的PHP有关问题
新手问个很简单的PHP问题
一维数组
怎么随机提取3个值并且保留键值
要最效率最简单的
还有问个附加小问题 怎么随机打乱一个一维数组 并且键值不变
------解决方案--------------------
- PHP code
<?php function kshuffle(&$array) { if(!is_array($array) || empty($array)) { return false; } $tmp = array(); foreach($array as $key => $value) { $tmp[] = array('k' => $key, 'v' => $value); } shuffle($tmp); $array = array(); foreach($tmp as $entry) { $array[$entry['k']] = $entry['v']; } return true; } <div class="clear"> </div>

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Most of the .tmp files are files left behind due to abnormal shutdown or crash. These temporary scratch disks have no use after you restart the computer, so you can safely delete them. When you use the Windows operating system, you may often find some files with the suffix TMP in the root directory of the C drive, and you will also find a TEMP directory in the Windows directory. TMP files are temporary files generated by various software or systems. , also known as junk files. Temporary files generated by Windows are essentially the same as virtual memory, except that temporary files are more targeted than virtual memory and only serve a certain program. And its specificity has caused many novices to be intimidated by it and not delete it.

1. The difference between Iterator and foreach is the polymorphic difference (the bottom layer of foreach is Iterator) Iterator is an interface type, it does not care about the type of collection or array; both for and foreach need to know the type of collection first, even the type of elements in the collection; 1. Why is it said that the bottom layer of foreach is the code written by Iterator: Decompiled code: 2. The difference between remove in foreach and iterator. First, look at the Alibaba Java Development Manual, but no error will be reported in case 1, and an error will be reported in case 2 (java. util.ConcurrentModificationException) first

The steps for PHP to determine the number of the foreach loop: 1. Create an array of "$fruits"; 2. Create a counter variable "$counter" with an initial value of 0; 3. Use "foreach" to loop through the array, and Increase the value of the counter variable in the loop body, and then output each element and their index; 4. Output the value of the counter variable outside the "foreach" loop to confirm which element the loop reaches.

The usage of return in C language is: 1. For functions whose return value type is void, you can use the return statement to end the execution of the function early; 2. For functions whose return value type is not void, the function of the return statement is to end the execution of the function. The result is returned to the caller; 3. End the execution of the function early. Inside the function, we can use the return statement to end the execution of the function early, even if the function does not return a value.

In Linux, tmp refers to a folder that stores temporary files. This folder contains temporary files created by the system and users; the default time limit of the tmp folder is 30 days. Files under tmp that are not accessed for 30 days will be automatically deleted by the system. of.

There is a lot of garbage in the tmp directory in the centos7 system. If you want to clear the garbage, how should you do it? Let’s take a look at the detailed tutorial below. To view the list of files in the tmp file directory, execute the command cdtmp/ to switch to the current file directory of tmp, and execute the ll command to view the list of files in the current directory. As shown below. Use the rm command to delete files. It should be noted that the rm command deletes files from the system forever. Therefore, it is recommended that when using the rm command, it is best to give a prompt before deleting the file. Use the command rm-i file name, wait for the user to confirm deletion (y) or skip deletion (n), and the system will perform corresponding operations. As shown below.

Source code: publicclassReturnFinallyDemo{publicstaticvoidmain(String[]args){System.out.println(case1());}publicstaticintcase1(){intx;try{x=1;returnx;}finally{x=3;}}}#Output The output of the above code can simply conclude: return is executed before finally. Let's take a look at what happens at the bytecode level. The following intercepts part of the bytecode of the case1 method, and compares the source code to annotate the meaning of each instruction in

The "tmp" file is a temporary file, usually generated by the operating system or program during operation, and is used to store temporary data or intermediate results when the program is running. These files are mainly used to help the program execute smoothly, but they are usually automatically deleted after the program is executed. tmp files can usually be found in the root directory of the C drive on Windows systems. However, tmp files are associated with a specific application or system, so their specific content and purpose may vary from application to application.
