8 Essential PHP function development and php_PHP tutorials

8 Essential PHP function development and php. The eight essential PHP function development tools should be clear to programmers who need phpPHP development. PHP has many built-in functions that can help you better develop PHP, 8 Essential PHP function development and php

PHP developers should be clear that PHP has many built-in functions that can help you better develop PHP. This article will share eight necessary PHP functions, all of them are very practical. I hope all PHP developers can master them.

1. pass any number of function parameters
In. NET or JAVA programming, the number of function parameters is fixed, but PHP allows you to use any number of parameters. The following example shows the default parameters of the PHP function:

// Function foo ($ arg1 = ", $ arg2 =") {echo "arg1: $ arg1 \ n"; echo "arg2: $ arg2 \ n ";} foo ('helloarg2, 'World');/* output: arg1: helloarg2: world */foo ();/* output: arg1: arg2 :*/

The following example shows the variable parameter usage of PHP. it uses the func_get_args () method:

// Yes, the parameter list is empty function foo () {// get all input parameter arrays $ args = func_get_args (); foreach ($ args as $ k =>$ v) {echo "arg ". ($ k + 1 ). ": $ v \ n" ;}} foo ();/* no output */foo ('Hello');/* output arg1: hello */foo ('hello', 'World', 'Again ');/* output arg1: helloarg2: worldarg3: again */

2. use glob () to find files
The function names of most PHP functions can be understood literally, but when you see glob (), you may not know what it is used for. In fact, glob () like scandir (), it can be used to find files. See the following usage:

// Obtain all files suffixed with PHP $ files = glob ('*. php '); print_r ($ files);/* output: Array ([0] => phptest. php [1] => pi. php [2] => post_output.php [3] => test. php) */You can also find a variety of extensions: // Retrieve the php file and TXT file $ files = glob ('*. {php, txt} ', GLOB_BRACE); print_r ($ files);/* output: Array ([0] => phptest. php [1] => pi. php [2] => post_output.php [3] => test. php [4] => log.txt [5] => test.txt 13 .) */

You can also add the following path:

$ Files = glob ('.. /images/*. jpg '); print_r ($ files);/* output: Array ([0] => .. /images/apple.jpg [1] => .. /images/art.jpg )*/

If you want to obtain the absolute path, you can call the realpath () function:

$files = glob(‘../images/a*.jpg'); // applies the function to each array element $files = array_map(‘realpath',$files); print_r($files); /* output looks like:Array([0] => C:\wamp\www\images\apple.jpg[1] => C:\wamp\www\images\art.jpg)*/ 

3. obtain memory usage information
The memory recycle mechanism of PHP is very powerful. you can also use the PHP script to obtain the current memory usage, call the memory_get_usage () function to obtain the current memory usage, and call memory_get_peak_usage () function to obtain the peak memory usage. The reference code is as follows:

Echo "Initial:". memory_get_usage (). "bytes \ n";/* output Initial: 361400 bytes * // memory usage for ($ I = 0; $ I <100000; $ I ++) {$ array [] = md5 ($ I) ;}// delete half of the memory for ($ I = 0; $ I <100000; $ I ++) {unset ($ array [$ I]);} echo "Final:". memory_get_usage (). "bytes \ n";/* printsFinal: 885912 bytes */echo "Peak:". memory_get_peak_usage (). "bytes \ n";/* output Peak: 13687072 bytes */

4. obtain CPU usage information
You can use getrusage () of PHP to obtain the CPU usage. this method is unavailable in windows.

Print_r (getrusage ()); /* output Array ([ru_oublock] => 0 [ru_inblock] => 0 [ru_msgsnd] => 2 [ru_msgrcv] => 3 [ru_maxrss] => 12692 [ru_ixrss] => 764 [ru_idrss] => 3864 [ru_minflt] => 94 [ru_majflt] => 0 [ru_nsignals] => 1 [ru_nvcsw] => 67 [ru_nivcsw] => 4 [ru_nswap => 0 [ru_utime. TV _usec] => 0 [ru_utime. TV _sec] => 0 [ru_stime. TV _usec] => 6269 [ru_stime. TV _sec] => 0) */

This structure seems obscure unless you know the CPU. The following are some explanations:
Ru_oublock: block output operation
Ru_inblock: block input operation
Ru_msgsnd: Sent message
Ru_msgrcv: Received message
Ru_maxrss: the largest and smallest resident set
Ru_ixrss: all shared memory size
Ru_idrss: all non-shared memory sizes
Ru_minflt: page recycling
Ru_majflt: The page is invalid.
Ru_nsignals: Received signal
Ru_nvcsw: active context switching
Ru_nivcsw: passive context switching
Ru_nswap: Swap Zone
Ru_utime. TV _usec: User state Time (microseconds)
Ru_utime. TV _sec: User State time (seconds)
Ru_stime. TV _usec: System Kernel time (microseconds)
Ru_stime. TV _sec: System Kernel time? (Seconds)
To see how much CPU your script consumes, we need to look at the values of "user-mode time" and "system kernel time. Second and microsecond are provided separately. you can divide the microsecond value by 1 million and add it to the second value to obtain the number of seconds with a decimal part.

// Sleep for 3 seconds (non-busy) sleep (3); $ data = getrusage (); echo "User time:". ($ data ['Ru _ utime. TV _sec '] + $ data ['Ru _ utime. TV _usec ']/1000000); echo "System time:". ($ data ['Ru _ stime. TV _sec '] + $ data ['Ru _ stime. TV _usec ']/1000000);/* output User time: 0.011552 System time: 0 */sleep does not occupy the System time. let's take a look at the following example: // loop 10 million times (busy) for ($ I = 0; $ I <10000000; $ I ++) {}$ data = getrusage (); echo "User time: ". ($ data ['Ru _ utime. TV _sec '] + $ data ['Ru _ utime. TV _usec ']/1000000); echo "System time:". ($ data ['Ru _ stime. TV _sec '] + $ data ['Ru _ stime. TV _usec ']/1000000);/* output User time: 1.424592 System time: 0.004204 */

This took about 14 seconds of CPU time, almost all of which were user time, because there was no system call.
The system time is the time when the CPU spends executing kernel commands on system calls. The following is an example:

$start = microtime(true); // keep calling microtime for about 3 seconds while(microtime(true) – $start < 3) { } $data = getrusage(); echo “User time: “. ($data['ru_utime.tv_sec'] + $data['ru_utime.tv_usec'] / 1000000); echo “System time: “. ($data['ru_stime.tv_sec'] + $data['ru_stime.tv_usec'] / 1000000); /* printsUser time: 1.088171System time: 1.675315*/

We can see that the above example consumes more CPU.
5. obtain system constants
PHP provides very useful system constants for you to get the current row number (_ LINE _), FILE (_ FILE _), Directory (_ DIR __), FUNCTION name (_ FUNCTION _), CLASS name (_ CLASS _), METHOD name (_ METHOD _), and NAMESPACE (_ NAMESPACE __), similar to C language.
We can think that these things are mainly used for debugging, but they are not necessarily the same. for example, we can use them when include other files? _ FILE _ (of course, you can also use _ DIR _ after PHP 5.3). The following is an example.

// this is relative to the loaded script's path // it may cause problems when running scripts from different directories require_once(‘config/database.php'); // this is always relative to this file's path // no matter where it was included from require_once(dirname(__FILE__) . ‘/config/database.php');

The following uses _ LINE _ to output some debug information, which helps you debug the program:

// Some code //... My_debug ("some debug message", _ LINE _);/* output Line 4: some debug message * // some more code //... My_debug ("another debug message", _ LINE _);/* output Line 11: another debug message */function my_debug ($ msg, $ line) {echo "Line $ line: $ msg \ n ";}

6. generate a unique id
Many friends use md5 () to generate a unique number, but md5 () has several disadvantages: 1. unordered, resulting in a decline in database sorting performance. 2. it is too long and requires more storage space. In fact, PHP comes with a function to generate a unique id. This function is uniqid (). The usage is as follows:

// Generate unique string echo uniqid ();/* output 4bd67c947233e * // generate another unique string echo uniqid ();/* output 4bd67c9472340 */

This algorithm is generated based on the CPU time stamp. Therefore, the first few digits of the id are the same in a similar period of time, which facilitates id sorting. if you want to avoid duplication, you can add a prefix before the id, for example:

// Prefix echo uniqid ('foo _ ');/* output foo_4bd67d6cd8b8f * // more entropy echo uniqid (", true);/* output 4bd67d6cd8b926. 12135106 * // all have echo uniqid ('Bar _ ', true);/* output bar_4bd67da1_b2.16.43664647 */

7. serialization
PHP Serialization functions are often used. when you need to store data in a database or file, you can use serialize () and unserialize () in PHP () method to achieve serialization and deserialization, the code is as follows:

// A complex array $ myvar = array ('hello', 42, array (1, 'two'), 'apple '); // serialize $ string = serialize ($ myvar); echo $ string;/* output a: 4: {I: 0; s: 5: "hello"; I: 1; i: 42; I: 2; a: 2: {I: 0; I: 1; I: 1; s: 3: "two";} I: 3; s: 5: "apple";} * // reverse sample $ newvar = unserialize ($ string); print_r ($ newvar ); /* output Array ([0] => hello [1] => 42 [2] => Array ([0] => 1 [1] => two) [3] => apple )*/

How to serialize data to json format? rest assured that php is ready for you. users who use php 5.2 or later can use the json_encode () and json_decode () functions to serialize data in json format, the code is as follows:

// a complex array$myvar = array( ‘hello', 42, array(1,'two'), ‘apple' ); // convert to a string $string = json_encode($myvar); echo $string; /* prints["hello",42,[1,"two"],”apple”]*/ // you can reproduce the original variable $newvar = json_decode($string); print_r($newvar); /* printsArray([0] => hello[1] => 42[2] => Array([0] => 1[1] => two)[3] => apple)*/

8. string compression
When we talk about compression, we may think of file compression. In fact, strings can also be compressed. PHP provides gzcompress () and gzuncompress () functions:

$ String = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. nunc ut elit id mi ultricies adipiscing. nulla facilisi. praesent pulvinar, sapien vel feugiat vestibulum, nulla dui presponorci, non ultricies elit lacus quis ante. lorem ipsum dolor sit amet, consectetur adipiscing elit. aliquam prepolicullamcorper urna quis iaculis. etiam ac massa sed turpis tempor luctus. curabitur sed nibh eu elit mollis congue. praesent ipsum diam, consectetur vitae ornare a, aliquam a nunc. in id magna pellentesque tellus posuere adipiscing. sed non mi metus, at lacinia augue. sed magna nisi, ornare in mollis in, mollis sed nunc. etiam at justo in leo congue mollis. nullam in neque eget metus hendrerit scelerisque eu non enim. ut malesuada lacus eu nulla bibendum id euismod urna sodales. "; $ compressed = gzcompress ($ string); echo" Original size: ". strlen ($ string ). "\ n";/* Original output size Original size: 800 */echo "Compressed size:". strlen ($ compressed ). "\ n";/* output Compressed size compressed: 418 * // decompress $ original = gzuncompress ($ Compressed );

The compression ratio is almost 50%. At the same time, you can use the gzencode () and gzdecode () functions to compress, instead of using different compression algorithms.
The above eight PHP functions are essential for development. are they all very practical?

Programmers in PHP development should be clear that PHP has many built-in functions and they can help you develop PHP more easily ,...