10 Little-Known But Very Useful PHP Functions

This article introduces 10 little-known but very useful PHP functions, which have certain reference value. Now I share them with you. Friends in need can refer to them

1.String distance (string similarity)

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<?php
$str1 = "aaa";
$str2 = "aaab";
echo levenshtein($str1, $str2); //输出2
?>

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It can calculate the string str1 There are several letters different from the string str2. This is a relatively unique function of PHP, because if you use other languages, you may have to implement the matrix calculation of the distance by yourself.

2. Return an array of all variables defined

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<?php
print_r(get_defined_vars());
?>

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This is a very useful feature when you want to debug your code and the code is messy and you forget which variables are defined. It returns an array of all variables defined. Put it in the last sentence~~~

3. Check your PHP code syntax function

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php_check_syntax is this function. However, it was deprecated in php5, otherwise it is still very useful to use php to develop an online compiler. Of course, you can also use php4.

4. Ignore abort requests from the client

<?php
$error_message = "";
$filename = "./php_script.php";
if(!php_check_syntax($filename,
      &$error_message)) 
 {
   echo "Errors were found in the file
    $filename: $error_message";
 }
 else
 {
   echo "The file $filename contained no syntax errors";
  }
?>

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General case Under this condition, the user can press "Stop" in the browser to stop all requests, but this function can ignore the user's operation.

5.高亮语法标记

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<?php
highlight_string(&#39; <?php phpinfo(); ?>&#39;);
highlight_string(&#39;<?php aa();?>&#39;);
?>

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这个其实再做一些特定语法展现时比较有用,它自动会输出 字符串，并显示蓝色代表高亮。

6.highlight_file（）高亮文件内容语法标记

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<?php
highlight_file("test.php"); 
//这里必须是一个存在的文件名
?>

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这个函数会把test.php文件内容加载出来，然后把里面的内容进行 高亮展示，很牛逼哦~~~

7.去掉文件中的注释和空格

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<?php 
 echo php_strip_whitespace("test.php");
?>

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这个函数作用巨大，如果你写完test.php程序后 不想让你的2B同事偷学，你可以用这个函数把去掉注释和空格的程序输出到页面，然后再拷贝回去。好比压缩功能。

8.在服务器端读取客户浏览器版本信息

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<?php
echo $_SERVER[&#39;HTTP_USER_AGENT&#39;];
 //输出常见的浏览器信息，譬如 Mozilla/5.0 (Windows NT 5.2; rv:26.0) Gecko/20100101 Firefox/26.0
$browser = get_browser(); 
print_r($browser);
?>

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注意：browscap.ini文件 请到网上去下载最新,文件里面记录了所有已存在的浏览器的类型及其信息，并在php.ini增加文件指向配置。这个文件可以帮你比较精准的判断用户当前浏览器的版本信息。

9.检查性能和cpu使用效率

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试一试便可，可以检查出你写的代码是否 蹂躏了服务器。遗憾的是这些函数不能在windows服务器上使用。（其实很正常嘛)

10.压缩字符串函数

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$string =
"这里放一大堆中文字，反正很长很长很长 ";
$compressed = gzcompress($string);//压缩
echo $compressed; //乱码了。是gzip压缩码了
$original = gzuncompress($compressed); 
//解压
echo $original;//正常了

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这个功能很有用，譬如你要写一些ajax在客户端和服务端进行无节操交互时，适当用一些这个函数还是很好地。（函数虽好，但是不要乱用哦，过于频繁对服务器性能也是有影响的）

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