Very useful PHP functions

This article mainly shares with you very useful PHP functions. These functions are not commonly used, but they are very useful. I hope they can help you.

1. sys_getloadavg()
sys_getloadavt() can obtain the system load status. This function returns an array containing three elements, each element representing the average load of the system over the past 1, 5, and 15 minutes. Rather than letting the server crash due to excessive load, it is better to actively die a script when the system load is very high. sys_getloadavg() is used to help you achieve this function. Unfortunately, this function is not valid under Windows.
2. pack()
Pack() can convert the 32-bit hexadecimal string returned by md5() into a 16-bit binary string, which can save storage space.
3. cal_days_in_month()
cal_days_in_month() can return the number of days in the specified month.
4. _()
WordPress developers often see this function, as well as _e(). These two functions have the same function and can be used in combination with the gettext() function to achieve multilingualization of the website. For details, please refer to the relevant parts of the PHP manual.
5. get_browser()
Isn’t it good to see what the user’s browser can do before sending the page? get_browser() can get the user's browser type and the functions supported by the browser, but first you need a php_browscap.ini file to serve as a reference file for the function.
It should be noted that this function’s judgment of browser functions is based on the general characteristics of this type of browser. For example, if the user has turned off JavaScript support in the browser, the function has no way of knowing this. However, this function is still very accurate in determining browser type and OS platform.
6. debug_print_backtrace()
This is a function used for debugging, which can help you find logical errors in the code. To understand this function, let’s look at an example:

$a = 0;
function iterate() {
global $a;
if( $a < 10 )
recur();
echo $a . “, “;
}
function recur() {
global $a;
$a++;
// how did I get here?
echo “\n\n\n”;
debug_print_backtrace();
if( $a < 10 )
iterate();
}
iterate();
# OUTPUT:
#0 recur() called at [C:\htdocs\php_stuff\index.php:8]
#1 iterate() called at [C:\htdocs\php_stuff\index.php:25]
#0 recur() called at [C:\htdocs\php_stuff\index.php:8]
#1 iterate() called at [C:\htdocs\php_stuff\index.php:21]
#2 recur() called at [C:\htdocs\php_stuff\index.php:8]
#3 iterate() called at [C:\htdocs\php_stuff\index.php:25]
#0 recur() called at [C:\htdocs\php_stuff\index.php:8]
#1 iterate() called at [C:\htdocs\php_stuff\index.php:21]
#2 recur() called at [C:\htdocs\php_stuff\index.php:8]
#3 iterate() called at [C:\htdocs\php_stuff\index.php:21]
#4 recur() called at [C:\htdocs\php_stuff\index.php:8]
#5 iterate() called at [C:\htdocs\php_stuff\index.php:25]  
7. metaphone()
这个函数返回单词的metaphone值，相同读音的单词具有相同的metaphone值，也就是说这个函数可以帮你判断两个单词的读音是否 相同。
8. natsort()
natsort()能将一个数组以自然排序法 进行排列，直接看个例子吧：
$items = array(
“100 apples”, “5 apples”, “110 apples”, “55 apples”
);
// normal sorting:
sort($items);
print_r($items);
# Outputs:
# Array
# (
# [0] => 100 apples
# [1] => 110 apples
# [2] => 5 apples
# [3] => 55 apples
# )
natsort($items);
print_r($items);
# Outputs:
# Array
# (
# [2] => 5 apples
# [3] => 55 apples
# [0] => 100 apples
# [1] => 110 apples
# )  
9. levenshtein()
Levenshtein()告诉你两个单词之间的“距离”。它告诉你如果想把一个单词变成另一个单词，需要插入、替换和删除多少字母。
看个例子吧：
$dictionary = array(
“php”, “javascript”, “css”
);
$word = “japhp”;
$best_match = $dictionary[0];
$match_value = levenshtein($dictionary[0], $word);
foreach($dictionary as $w) {
$value = levenshtein($word, $w);
if( $value < $match_value ) {
$best_match = $w;
$match_value = $value;
}
}
echo “Did you mean the ‘$best_match’ category?”;  
10. glob()
glob()会让你觉得用 opendir(), readdir()和closedir()来寻找文件非常蠢。
foreach (glob(“*.php”) as $file)
echo “$file\n”;

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