8 essential PHP functions for development, essential php_PHP tutorial

8 essential PHP functions for development, essential php

Programmers who have done PHP development should know that there are many built-in functions in PHP. If you master them, you can To help you become more comfortable in 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:
 */

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
 */

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 search for 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 a variety of 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 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

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 &ldquo;Final: &ldquo;.memory_get_usage().&rdquo; bytes \n&rdquo;;
 /* prints
 Final: 885912 bytes
 */

echo &ldquo;Peak: &ldquo;.memory_get_peak_usage().&rdquo; bytes \n&rdquo;;
 /* 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. 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: All 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 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);

/* 输出
User time: 0.011552
 System time: 0
 */

Sleep does not occupy system time. We can look at the following example:

// loop 10 million times (busy)
 for($i=0;$i<10000000;$i++) {

}

$data = getrusage();
 echo &ldquo;User time: &ldquo;.
 ($data['ru_utime.tv_sec'] +
 $data['ru_utime.tv_usec'] / 1000000);
 echo &ldquo;System time: &ldquo;.
 ($data['ru_stime.tv_sec'] +
 $data['ru_stime.tv_usec'] / 1000000);

/* 输出
User time: 1.424592
 System time: 0.004204
 */

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) &ndash; $start < 3) {

}

$data = getrusage();
 echo &ldquo;User time: &ldquo;.
 ($data['ru_utime.tv_sec'] +
 $data['ru_utime.tv_usec'] / 1000000);
 echo &ldquo;System time: &ldquo;.
 ($data['ru_stime.tv_sec'] +
 $data['ru_stime.tv_usec'] / 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__), 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 .

// 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 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”;
 }

　6. Generate a unique id

Many friends use md5() to generate unique numbers, but md5() has several shortcomings: 1. Disorder, 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(). Here’s how to use it:

// 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 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
 */

7. Serialization

PHP serialization function may be used 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
 )
 */

　　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。

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