php string

This article introduces the content of PHP strings, which has certain reference value. Now I share it with everyone. Friends in need can refer to

iconv_strlen to get the number of characters
// Assume that the current page encoding is GBK

<?php
$str="中国abc";
echo strlen($str); //返回7,因为 GBK编码每个中文两个字节，strlen是返回字符串所占的字节长度。
echo "<hr>";
echo iconv_strlen($str,"GBK"); //返回5.iconv_strlen 是统计字符串的字符数量
?>

//Assume that the current page encoding is UTF-8

<?php
$str="中国abc";
echo strlen($str); //返回9,因为 UTF-8编码每个中文三个字节，strlen是返回字符串所占的字节长度。
echo "<hr>";
echo iconv_strlen($str,"UTF-8"); //返回5.iconv_strlen 是统计字符串的字符数量
?>

iconv_strlen can calculate the accurate number of characters no matter what encoding it is. number.

mb_strlen — Get the length of a string
PHP’s built-in string length function strlen cannot handle Chinese strings correctly. It only gets the number of bytes occupied by the string.
For GB2312 Chinese encoding, the value obtained by strlen is 2 times the number of Chinese characters, while for UTF-8 encoded Chinese, the difference is 3 times (under UTF-8 encoding, one Chinese character occupies 3 characters Festival).
Using the mb_strlen function can better solve this problem.
The usage of mb_strlen is similar to strlen, except that it has a second optional parameter to specify the character encoding.
For example, to get the UTF-8 string $str length, you can use mb_strlen($str,'UTF-8').
If the second parameter is omitted, PHP's internal encoding will be used. The internal encoding can be obtained through the mb_internal_encoding() function.
It should be noted that mb_strlen is not a core function of PHP. Before using it, you need to make sure that php_mbstring.dll is loaded in php.ini, that is, make sure that the line "extension=php_mbstring.dll" exists and has not been commented out, otherwise it will An undefined function problem occurred.
mb_strlen('abcdef','utf-8') and mb_strlen('one two three four five six', 'utf-8') are both equal to 6

trim
echo trim(" ,1,2,3,4,", ","); // You will get 1,2,3,4 with the "," numbers at both ends cut off.

strcmp() function compares two strings.
Note: The strcmp() function is binary safe and case-sensitive.
This function returns:
0 - If the two strings are equal
<0 - If string1 is less than string2
>0 - If string1 is greater than string2

HTML related
1,htmlspecialchars($string)
This is its simplest usage, converting some special characters (as the name suggests) &,',"<,> in the string into their corresponding HTML entity forms:
PHP:

  $str = "i love kiki, iwind said.";
    echo htmlspecialchars($str);

will output
i love kiki, iwind said.
2,htmlentities($string )
Convert all characters that can be converted into entity form into entity form.
3,html_entity_decode($string);
Added after PHP4.3.0, it has the opposite function to htmlentities($string).
4,nl2br($string)
Convert all newline characters in the string into
newline characters. For example:

 PHP:
    $str = "i love kiki,/n iwind said.";
    echo nl2br($str);

will output
i love kiki,
iwind said.

Related recommendations:

Detailed explanation of PHP string encoding issues


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