Summary of 9 commonly used functions in PHP development

1. Any number of parameters for a function
You may know that PHP allows you to define a function with default parameters. But you may not know that PHP also allows you to define a function with completely arbitrary parameters
Here is an example to show you a function with default parameters:

Copy code The code is as follows:

 
 // Function with two default parameters 
 function foo($arg1 = '', $arg2 = '') { 
 echo "arg1: $arg1n"; 
 echo "arg2: $arg2n"; 
} 
 foo('hello','world'); 
 /* Output: 
 arg1: hello 
 arg2 : world 
 */ 
 foo(); 
 /* Output: 
 arg1: 
 arg2: 
*/ 
 Now let’s take a look at a function with variable parameters , which uses the ?func_get_args() method: 
　// Yes, the formal parameter list is empty
　function foo() { 
　// Get an array of all incoming parameters
　$args = func_get_args(); 
 foreach ($args as $k => $v) { 
 echo "arg".($k+1).": $vn"; 
　} 
　} 
 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
Many PHP functions have a relatively long self-explanatory function name, but when you see ?glob(), you may You don't know what this function is used for, unless you are already familiar with it.
You can think of this function as scandir(), which can be used to find files.

Copy code The code is as follows:

 
　 // Get all files with the suffix 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 search for a variety of suffixes
 // Get PHP files 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 path: 
　$ files = glob('../images/a*.jpg'); 
print_r($files); 
/* Output: 
Array 
( 
[0] => ../images/apple.jpg 
　[1] => ../images/art.jpg 
　) 
　*/ 
　If you want to get the absolute path, you can call ?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:wampwwwimagesapple.jpg 
　[1] => C:wampwwwimagesart.jpg 
　) 
　*/ 

　3. Memory usage information
Observing the memory usage of your program allows you to better optimize it your code.
PHP has a garbage collection mechanism and a very complex memory management mechanism. You can find out how much memory your script is using. To know the current memory usage, you can use the memory_get_usage() function. If you want to know the peak memory usage, you can call the memory_get_peak_usage() function.

Copy code The code is as follows:

echo "Initial: ".memory_get_usage()." bytes n";
/* Output
Initial: 361400 bytes
*/
// Use memory
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"; .memory_get_peak_usage()." bytes n";
　/* Output peak value
　Peak: 13687072 bytes
　*/

　4. CPU usage information
Using the ?getrusage() function can let you know the CPU usage. Note that this feature is not available under Windows.

Copy code The code is as follows:

 
　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] => > 1 
　[ru_nvcsw] => 67 
　[ru_nivcsw] => .tv_sec] => 0 
　[ru_stime.tv_usec] => 6269 
　[ru_stime.tv_sec] => 0 
　) 
　*/ 
　This structure looks very obscure. , unless you know a lot about CPU. Some explanations below: 
 ru_oublock: block output operation 
 ru_inblock: block input operation 
 ru_msgsnd: message sent 
 ru_msgrcv: message received 
 ru_maxrss: maximum resident set size 
 ru_ixrss: Total shared memory size 
 ru_idrss: Total non-shared memory size 
 ru_minflt: Page recycling 
 ru_majflt: Page invalidation 
 ru_nsignals: Signals received 
 ru_nvcsw: Active context switch 
 ru_nivcsw: passive context switching 
 ru_nswap: swap area 
 ru_utime.tv_usec: user mode time (microseconds) 
 ru_utime.tv_sec: user mode 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". The seconds and microseconds parts are provided separately. You can divide the microseconds value by 1 million and add it to the seconds value to get the number of seconds with a fractional 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 system time, we can Let’s 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: “. : 0.004204 
　*/ 

 
 This took about 14 seconds of CPU time, almost all of it user time since there were no system calls. 
 System time is the time the CPU spends executing kernel instructions on system calls. Here is an example: 



Copy code

 The code is as follows:

　$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' ); 🎜>We can see that the above example consumes more CPU.
　
5. System constants

　PHP provides very useful system constants that allow you to get the current line number (__LINE__), file (__FILE__), directory (__DIR__), and function name (__FUNCTION__) , class name (__CLASS__), method name (__METHOD__) and namespace (__NAMESPACE__), much like C language.
We can think that these things are mainly used for debugging, but that is not necessarily the case. For example, we can use ?__FILE__ when including other files (of course, you can also use __DIR__ after PHP 5.3). Here is an example .

Copy code

The code is as follows:

 
// 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 is the output using __LINE__ Some debug information to help 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: $msgn"; 
} 
  6. Generate a unique ID 
 Many people use md5() to generate a unique ID, as shown below: 
 // generate unique string 
 echo md5(time() . mt_rand(1, 1000000)); 
 Actually, there is a function called ?uniqid() in PHP that is specifically used to do this: 
 // generate unique string 
 echo uniqid(); 
 /* Output 
　4bd67c947233e 
　*/ 
　// generate another unique string 
　echo uniqid(); 
　/* Output 
　4bd67c9472340 
 The first few digits of the IDs that come out are the same. This is because the generator depends on the system time. This is actually a very good feature because you can easily sort your IDs. MD5 cannot do this. 
 You can also add a prefix to avoid duplication of names: 
 // Prefix 
 echo uniqid('foo_'); 
 /* Output 
 foo_4bd67d6cd8b8f 
 */ 
 // There is more entropy
　echo uniqid('',true); 
　/* Output
　4bd67d6cd8b926.12135106 
　*/ 
　// Both have
　echo uniqid('bar_' ,true); 
　/* Output
　bar_4bd67da367b650.43684647 
　*/ 

 

　 Moreover, the generated ID will be shorter than that generated by MD5, which will save you a lot. space.
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Time: 2011-07-08 00:18 Source: coolshell.cn Author: coolshell.cn Clicks: 5403 times [Font size: Large, Medium, Small] 1. Any number of parameters for a function You may know that PHP allows you to define a default Parameter function. But you may not know that PHP also allows you to define a function with completely arbitrary parameters. Here is an example showing you a function with default parameters: // Function with two default parameters function foo($arg1 = '', $arg2 = '') { echo arg1: $ar
　
7. Serialization
Will you save a more complex data structure into a database or file? You don’t need to do it yourself Write your own algorithm. PHP has already done it for you, it provides two functions: ?serialize() and unserialize():
　

Copy code 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";} 
　*/ 
　//Deserialization
　$newvar = unserialize($string); 
　print_r($newvar); 
　/* Output
　Array 
　( 
　[0] => hello 
　[1] => 42 
　[2] => Array 
　( 
　[0] => 1 
　[1] => two 
　) 
　[3] => apple 
　) 
　*/ 
　This is a native function of PHP, however today JSON is becoming more and more The more popular it is, so after PHP5.2, PHP starts to support JSON. You can use the json_encode() and json_decode() functions 
　// 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); => 42 
　[2] => Array 
　( 
　[0] => 1 
　[1] => two 
　) 
　[3] => ; apple 
　) 
　*/ 

 
　 This looks more compact and is compatible with Javascript and other languages. But for some very complex data structures, data loss may occur. 
　
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: 

Copy code
The code is as follows:

　$string = "Lorem IPSUM DOLORR SIT AMET, Consectetur Adipiscip Elit. Nunc Ut Elit ID Mi Ultricies Adipiscing. Nulla Facilisi. SAPIEN VEL FEUGIAT VESTIBULUM, NULLA DUI PRETIUM Orci,

Non Ultricies Elit lacus quis ante. Lorem ipsum dolor

sit amet, consectetur adipiscing elit. Aliquam
pretium ullamcorper urna quis iaculis. gue. Sed magna nisi, ornare in mollis in, mollis
　sed nunc. Etiam at justo in leo congue mollis. compressed = gzcompress($string);
echo "Original size: ". strlen($string)."n";
/* Output original size
Original size: 800
*/
Echo "Compressed size: ". strlen($compressed)."n";
/* Output the compressed size
Compressed size: 418
*/
// Decompress
$original = gzuncompress($compressed);

　 Almost 50% compression ratio. At the same time, you can also use the ?gzencode() and gzdecode() functions to compress, but they use different compression algorithms.
　
9. Register shutdown function

There is a function called ?register_shutdown_function() that allows you to run the code before the entire script is stopped. Let’s look at an example below:

Copy the code

The code is as follows:

 
 // capture the start time 
 $start_time = microtime(true); 
 // do some stuff 
 // ... 
 // display how long the script took 
 echo "execution took: ". 
 (microtime(true) - $start_time). 
 " seconds."; 
 The above example is just used to calculate the running time of a certain function. Then, if you call the ?exit() function in the middle of a function, your final code will not be run. Also, if the script is terminated in the browser (the user presses the stop button), it cannot be run. 
 And when we use register_shutdown_function(), your program will be run even after the script is stopped: 
 $start_time = microtime(true); 
 register_shutdown_function('my_shutdown'); 
 // do some stuff 
 // ... 
 function my_shutdown() { 
 global $start_time; 
 echo "execution took: ". 
 (microtime(true) - $ start_time). 
　" seconds."; 
　} 

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Summary of 9 commonly used functions in PHP development_PHP tutorial