8 essential PHP function development

This article mainly introduces eight essential PHP functions. For more information, see

This article mainly introduces eight essential PHP functions. For more information, see

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/*. 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: