8 essential PHP function development, essential php

Programmers who develop PHP should know that there are many built-in functions in PHP. Mastering them can help you To become more comfortable when doing PHP development, this article will share 8 essential PHP functions for development, all of which 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 generally fixed, but PHP allows you to use any number of parameters. The following example shows you the default parameters of a PHP function:

// 两个默认参数的函数 
function foo($arg1 = ”, $arg2 = ”) { 
echo “arg1: $arg1\n”; 
echo “arg2: $arg2\n”; 
} 
foo(‘hello','world'); 
/* 输出:
arg1: hello
arg2: world
*/ 
foo(); 
/* 输出:
arg1:
arg2:
*/

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The following example is the usage of variable parameters in PHP, which uses the func_get_args() method:

// 是的，形参列表为空 
function foo() { 
// 取得所有的传入参数的数组 
$args = func_get_args(); 
foreach ($args as $k => $v) { 
echo “arg”.($k+1).”: $v\n”; 
} 
} 
foo(); 
/* 什么也不会输出 */ 
foo(‘hello'); 
/* 输出
arg1: hello
*/ 
foo(‘hello', ‘world', ‘again'); 
/* 输出
arg1: hello
arg2: world
arg3: again
*/

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2. Use glob() to find files
The function names of most PHP functions can understand their purpose literally, but when you see glob(), you may not know what it is used for. In fact, glob() and scandir( ) can be used to find files, please see the following usage:

// 取得所有的后缀为PHP的文件 
$files = glob(‘*.php'); 
print_r($files); 
/* 输出:
Array
(
[0] => phptest.php
[1] => pi.php
[2] => post_output.php
[3] => test.php
)
*/
 
你还可以查找多种后缀名：
// 取PHP文件和TXT文件 
$files = glob(‘*.{php,txt}', GLOB_BRACE); 
print_r($files); 
/* 输出:
Array
(
[0] => phptest.php
[1] => pi.php
[2] => post_output.php
[3] => test.php
[4] => log.txt
[5] => test.txt
13.
)
*/

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You can also add the path:

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

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If you want to get 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
)
*/

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3. Get memory usage information
PHP's memory recycling mechanism is already very powerful. You can also use PHP scripts to obtain the current memory usage, call the memory_get_usage() function to obtain the current memory usage, and call the memory_get_peak_usage() function to obtain the peak memory usage. The reference code is as follows:

echo “Initial: “.memory_get_usage().” bytes \n”; 
/* 输出
Initial: 361400 bytes
*/ 
// 使用内存 
for ($i = 0; $i < 100000; $i++) { 
$array []= md5($i); 
} 
// 删除一半的内存 
for ($i = 0; $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”; 
/* 输出峰值
Peak: 13687072 bytes
*/

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4. Obtain CPU usage information
After obtaining the memory usage, you can also use PHP's getrusage() to obtain the CPU usage. This method is not available under Windows.

print_r(getrusage()); 
/* 输出
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
)
*/

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This structure seems very obscure, unless you know the CPU very well. 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 invalid
ru_nsignals: Received signals
ru_nvcsw: Active context switching
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 "User Mode Time" and "System Kernel Time" values. 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'] + 
$data['ru_stime.tv_usec'] / 1000000); 
/* 输出
User time: 0.011552
System time: 0
*/
sleep是不占用系统时间的，我们可以来看下面的一个例子： 
// loop 10 million times (busy) 
for($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); 
/* 输出
User time: 1.424592
System time: 0.004204
*/

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This took about 14 seconds of CPU time, almost all of which was 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:

$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
System time: 1.675315
*/

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We can see that the above example consumes more CPU.
5. Get system constants
PHP provides very useful system constants that allow you to get the current line number (__LINE__), file (__FILE__), directory (__DIR__), 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 not necessarily. 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.

// 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');

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The following is using __LINE__ to output some debug information, which will help you debug the program:

// some code 
// … 
my_debug(“some debug message”, __LINE__); 
/* 输出
Line 4: some debug message
*/ 
// some more code 
// … 
my_debug(“another debug message”, __LINE__); 
/* 输出
Line 11: another debug message
*/ 
function my_debug($msg, $line) { 
echo “Line $line: $msg\n”;
}

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6. Generate a unique id
Many friends use md5() to generate unique numbers, but md5() has several shortcomings: 1. Disorder, which leads to a decrease in sorting performance in the database. 2. Too long and requires more storage space. In fact, PHP comes with a function to generate a unique id. This function is uniqid(). Here’s how to use it:

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

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This algorithm is generated based on the CPU timestamp, so in a similar time period, the first few digits of the ID are the same, which also facilitates the sorting of IDs. If you want to better avoid duplication, you can precede the ID Add a prefix, such as:

// 前缀 
echo uniqid(‘foo_'); 
/* 输出
foo_4bd67d6cd8b8f
*/ 
// 有更多的熵 
echo uniqid(”,true); 
/* 输出
4bd67d6cd8b926.12135106
*/ 
// 都有 
echo uniqid(‘bar_',true); 
/* 输出
bar_4bd67da367b650.43684647
*/

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7. Serialization
You may use PHP serialization function more and more commonly. When you need to save data to a database or file, you can use the serialize() and unserialize() methods in PHP to achieve serialization and Deserialization, the code is as follows:

// 一个复杂的数组 
$myvar = array( 
‘hello', 
42, 
array(1,'two'), 
‘apple' 
); 
// 序列化 
$string = serialize($myvar); 
echo $string; 
/* 输出
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”;}
*/ 
// 反序例化 
$newvar = unserialize($string); 
print_r($newvar); 
/* 输出
Array
(
[0] => hello
[1] => 42
[2] => Array
(
[0] => 1
[1] => two
)
[3] => apple
)
*/

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How to serialize into json format? Don’t worry, PHP has already done it for you. Users using PHP 5.2 or above can use json_encode() and json_decode() functions to serialize 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
)
*/

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8、字符串压缩
当我们说到压缩，我们可能会想到文件压缩，其实，字符串也是可以压缩的。PHP提供了 gzcompress() 和gzuncompress() 函数：

$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 pretium orci, 
non ultricies elit lacus quis ante. Lorem ipsum dolor 
sit amet, consectetur adipiscing elit. Aliquam 
pretium ullamcorper 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($string).”\n”; 
/* 输出原始大小
Original size: 800
*/ 
echo “Compressed size: “. strlen($compressed).”\n”; 
/* 输出压缩后的大小
Compressed size: 418
*/ 
// 解压缩 
$original = gzuncompress($compressed);

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几乎有50% 压缩比率。同时，你还可以使用 gzencode() 和 gzdecode() 函数来压缩，只不用其用了不同的压缩算法。
以上就是8个开发必备的PHP功能，是不是都很实用呢？