(Php technology entry) 8 essential PHP function development

Programmers who have developed PHP should be clear that PHP has many built-in functions and can master them to help you better develop PHP, this article will share eight essential PHP functions, all of which are very practical and I hope all PHP developers can master them. Programmers who have developed PHP should be clear that PHP has many built-in functions and can master them to help you better develop PHP, this article will share eight essential PHP functions, all of which are very practical and 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:
 
// Functions with two default parameters
Function foo ($ arg1 = ", $ arg2 = "){
Echo "arg1: $ arg1 \ n ";
Echo "arg2: $ arg2 \ n ";
}
Foo ('hello', 'World ');
/* Output:
Arg1: hello
Arg2: 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 (){
// Obtain the array of all input parameters
$ Args = func_get_args ();
Foreach ($ args as $ k =>v v ){
Echo "arg". ($ k + 1). ": $ v \ n ";
}
}
Foo ();
/* Nothing will be output */
Foo ('Hello ');
/* Output
Arg1: hello
*/
Foo ('hello', 'World', 'Again ');
/* Output
Arg1: hello
Arg2: world
Arg3: 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 multiple extension names:


// Retrieve the PHP and TXT files
$ 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
)
*/
 
You can also add the following path:


$ Files = glob ('../images/a *. 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
Initialize: 361400 bytes
*/
// Memory usage
For ($ I = 0; I I <100000; $ I ++ ){
$ Array [] = md5 ($ I );
}
// Delete half of the memory
For ($ I = 0; I I <100000; $ I ++ ){
Unset ($ array [$ I]);
}
Echo "Final:". memory_get_usage (). "bytes \ n ";
/* Prints
Final: 885912 bytes
*/
Echo "Peak:". memory_get_peak_usage (). "bytes \ n ";
/* Output peak value
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] = & gt; 12692
[Ru_ixrss] = & gt; 764
[Ru_idrss] = & gt; 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] = & gt; 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 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
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 );
/* Prints
User time: 1.088171
Time: 1.675315
*/
 
We can see that the above example consumes more CPU.
 
5. obtain system constants
 
PHP provides very useful system constants, allowing you to get the current row number (_ LINE _), FILE (_ FILE _), Directory
(_ DIR _), FUNCTION name (_ FUNCTION _), CLASS name (_ CLASS _), METHOD name (_ METHOD _), and namespace
(_ NAMESPACE _), which is very similar to the 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 encoded ded 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_4bd67da% B %.4%4647
*/
 
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'
);
// Serialization
$ 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 );
/* Prints
Array
(
[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 size: 418
*/
// Extract
$ 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?