(Introduction to PHP technology) 8 essential PHP function development

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 which are very useful. Practical, I hope all PHP developers can master it.


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:

// 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:
*/
The following example is the usage of variable parameters in PHP, which uses the func_get_args() method:
// Yes, the formal parameter list is empty
function foo() {
// Get all the incoming parameters Array of
$args = func_get_args();
foreach ($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

The function names of most PHP functions can understand their purpose literally, but when you see When using 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:

// Get all the suffixes of PHP files
$files = glob('*.php');
print_r($files);
/* Output:
Array
(
[0] => phptest.php
[1] => pi.php
[2] => post_output.php
[3] => test.php
)
*/

You can also search for multiple suffix names:


// 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 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:wampwwwimagesapple.jpg
[1] => C:wampwwwimagesart.jpg
)
*/

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”;
/* Output
Initial: 361400 bytes
*/
// Use memory
for ($i = 0; $i $array []= md5($i);
}
// Delete half of the memory
for ($i = 0; $i unset($array[$i ]);
}
echo “Final: “.memory_get_usage().” bytes n”;
/* prints
Final: 885912 bytes
*/
echo “Peak: “.memory_get_peak_usage().” bytes n”;
/* Output peak
Peak: 13687072 bytes
*/

4. Obtain CPU usage information

To obtain 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());
/* 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] => 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: all shared memory size
ru_idrss: all non-shared Memory size
ru_minflt: Page recycling
ru_majflt: Page invalidation
ru_nsignals: Received signals
ru_nvcsw: Active context switch
ru_nivcsw: Passive context switch
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 "User "State 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);
/* output
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}
$data = getrusage();
echo “User time: “.
($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
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:
$start = microtime(true);
// keep calling microtime for about 3 seconds
while(microtime(true) – $start }
$data = getrusage();
echo "User time: ".
($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
*/

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');

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__);
/* 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 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(). The following is the usage:

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

This algorithm is generated based on CPU timestamps, so in similar time periods, 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 add a prefix before the ID. , such as:
// prefix
echo uniqid('foo_');
/* output
foo_4bd67d6cd8b8f
*/
// with more entropy
echo uniqid(”,true);
/* output
4bd67d6cd8 b926.12135106
*/
// Both have
echo uniqid('bar_',true);
/* Output
bar_4bd67da367b650.43684647
*/

7. Serialization

You may use the PHP serialization function more, and It is more common. When you need to save data to a database or file, you can use the serialize() and unserialize() methods in PHP to implement 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";}
*/
// Deserialization
$newvar = unserialize($string);
print_r($newvar );
/* Output
Array
(
[0] => hello
[1] => 42
[2] => Array
(
[0] => 1
[1] => two
)
[3] => apple
)
*/

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 the json_encode() and json_decode() functions to achieve this. Serialization 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 Thinking 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. bulum, Nulla dui pretium orci,
non ultricies elit lacus quis ante. Lorem ipsum dolor
sit amet, consectetur adipiscing elit. Aliquam
pretium ullamcorper urna quis iaculis. eu elit
mollis congue. Praesent ipsum diam, consectetur vitae
ornare a, aliquam a nunc. In id magna pellentesque
tellus posuere adipiscing. 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 compressed size
Compressed size: 418
*/
// Decompression
$original = gzuncompress($compressed);

Almost 50% compression ratio. At the same time, you can also use the gzencode() and gzdecode() functions to compress, just using different compression algorithms.

The above are 8 essential PHP functions for development. Are they all practical?