8 essential functions for PHP development

[Introduction] Programmers who have done PHP development should know that there are many built-in functions in PHP. Mastering them can help you become more comfortable in PHP development. This article will share 8 essential PHP functions for development. , all of them are very practical, I hope all PHP developers can master them. 1. Pass any number of functions

Programmers who have done PHP development should know that there are many built-in functions in PHP. Mastering them can help you become more comfortable when doing PHP development. This article will share 8 All of the PHP functions necessary for development are very practical. I hope all PHP developers can master them.

1. Pass any number of function parameters

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

// 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: 
*/  
下面这个示例是PHP的不定参数用法，其使用到了 func_get_args()方法：  
// 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 
*/

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(), like 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 
) 
*/

You can also search for multiple suffixes:

// 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 
) 
*/

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 
) 
*/

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:\wamp\www\images\apple.jpg 
[1] => C:\wamp\www\images\art.jpg 
) 
*/

3. Get memory usage information

PHP’s memory recycling mechanism is already very powerful. You can also use PHP scripts to get the current memory usage and call the memory_get_usage() function To obtain the current memory usage, 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 
*/

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 
) 
*/

This structure seems very obscure, unless you know the CPU very well. Here are some explanations:

• ru_oublock: block output operation

• ru_inblock: block input operation

• ru_msgsnd: Sent message

• ru_msgrcv: Received message

• ##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: 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 "user mode time" ” and the value of “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);  
/* 输出 
User time: 0.011552 
System time: 0 
*/

sleep does not take up system time. We can look at the following example:

// loop 10 million times (busy)  
for($i=0;$i<10000000;$i++) {  
}  
$data = getrusage();  
echo “User time: “.  
($data[&#39;ru_utime.tv_sec&#39;] +  
$data[&#39;ru_utime.tv_usec&#39;] / 1000000);  
echo “System time: “.  
($data[&#39;ru_stime.tv_sec&#39;] +  
$data[&#39;ru_stime.tv_usec&#39;] / 1000000);  
/* 输出 
User time: 1.424592 
System time: 0.004204 
*/

This took about 14 seconds of CPU time, almost all of which is the user's time. Because there are 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[&#39;ru_utime.tv_sec&#39;] +  
$data[&#39;ru_utime.tv_usec&#39;] / 1000000);  
echo “System time: “.  
($data[&#39;ru_stime.tv_sec&#39;] +  
$data[&#39;ru_stime.tv_usec&#39;] / 1000000);  
/* prints 
User time: 1.088171 
System time: 1.675315 
*/

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__), 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 not necessarily. For example, we can use ?__FILE__ when including other files (of course, you can also use __DIR__ after PHP 5.3), as follows 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 is to use __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”;  
}

6. Generate a unique id

Many friends use it md5() to generate a unique number, but md5() has several shortcomings: 1. Unordered, resulting in reduced 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(). The following is the usage:

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

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 is also convenient for sorting the ID, if you want to do better To avoid duplication, you can add a prefix before the id, 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 
*/

7, serialization

PHP序列化功能大家可能用的比较多，也比较常见，当你需要把数据存到数据库或者文件中是，你可以利用PHP中的serialize() 和 unserialize()方法来实现序列化和反序列化，代码如下：

// 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 
) 
*/

如何序列化成json格式呢，放心，php也已经为你做好了，使用php 5.2以上版本的用户可以使用json_encode() 和 json_decode() 函数来实现json格式的序列化，代码如下：

// 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、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);

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？

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