Commonly used string functions in php

This article mainly introduces the commonly used string functions in PHP. Friends who are interested can refer to it. I hope it will be helpful to everyone.

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• Determine the string length

• Compare strings

• Split connection inversion

• Convert html to strings

• Fill and remove strings

• Count the number of characters and words

• Find, replace and intercept

• Case processing

php has 98 built-in string functions (except functions based on regular expressions, regular expressions are not discussed here), which can handle every aspect that can be encountered in strings. This article explains the commonly used A brief summary of the string function, which mainly includes the following 8 parts: 1. Determine the length of the string, 2. Compare strings, 3. Split connection and reverse, 4. Convert html and strings to each other, 5. Fill and remove strings , 6. Count the number of characters and words, 7. Search, replace and intercept, 8. Case processing.

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Determine the string length

strlen function and mb_strlen function, the latter needs to enable the mbstring extension

<?php 
    header(&#39;content-type:text/html;charset=utf-8&#39;);
    $str = &#39;abcdef&#39;;    echo strlen($str); // 6
    echo "<br/>";
    $str = ' ab cd ';    echo mb_strlen($str); // 7
    echo "<br/>";    //strlen 是计算字符串"字节"长度 
    //mb_strlen,是根据编码,计算字符串的"字符"个数. 

    $str='中华人民共和国';    echo "字节长度是".strlen($str);//在 UTF-8编码下，一个汉字占3个字节 在gbk中一个汉字占2个字节
    echo "<br/>";    echo "字符长度是".mb_strlen($str,'utf-8'); ?>

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Compare strings

strcmp function, strcasecmp function, strspn function, strcspn function

<?php 
    $pwd="userpwd";
    $pwd2="Userpwd";    //区分大小写
    if (strcmp($pwd, $pwd2) !=0) {        echo "password do not match";
    } else{        echo "password match";
    }

    $email1="www.baidu.com";
    $email2="WWW.BAIDU.COM";    //不区分大小写
    if (!strcasecmp($email1, $email2)) {        echo "ok",&#39;<br>';
    }    //求两个字符串相同的部分
    $password="1233345";    if (strspn($password,"1234567890")==strlen($password)) {        echo "the password connot consist solely of numbers";
    }    //
    $password="a12345";    if (strcspn($password, "1234567890")==0) {        echo "the password connot consist solely of numbers";
    }    
 ?>

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Split connection reverse

str_split function, split function, explode function and implode function

<?php header(&#39;content-type:text/html;charset=utf-8&#39;);
    $str = "Hello Friend";

    $arr1 = str_split($str);
    print_r($arr1);

    $arr2 = str_split($str, 3);
    print_r($arr2);

    $str = &#39;abc,中国,美国,日本&#39;; 
    // explode,是根据指定的分割符,把字符串拆成数组. 
    $arr = explode(&#39;,&#39;,$str); 
    print_r($arr); 
    // implode,是根据指定的连接符,把数组再拼接成字符串 
    $arr = explode(&#39;,&#39;,$str); 
    echo implode(&#39;~&#39;,$arr),&#39;<br />'; 
    // 你可以只传一个数组做参数,不指定连接符, 
    // 这样,将把数组单元直接拼接起来 
    echo implode($arr); ?>

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Convert html to string

htmlspecialchars function, strip_tags function, get_html_translation_table function and addcslashes function and htmlentities function

<?php 

    $str = "hello &#39;, world"; 
    echo $str,&#39;<br />';    echo $str= addslashes($str),'<br />';    echo stripslashes($str),'<br />';
    $str = '<ab>'; 
    echo $str,'<br />'; 
    echo htmlspecialchars($str); 
    echo "</br>";
    $str="Email <a href=&#39;admin@qq.com&#39;>example@qq.com</a>";    echo strip_tags($str); ?>

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Filling and removing strings

trim function, ltrim function, rtrim function, str_pad function, chunk_split function

<?php 
    $str = &#39;12345678&#39;; 
    echo chunk_split($str,3,&#39;,&#39;);    echo "<br>";
    $text   = "\t\tThese are a few words :) ...  ";    echo trim($text);    echo "<br>";    echo ltrim($text,'\t'),'<br>';    echo rtrim($text,'\r'),'<br>';    echo str_pad('apple', 6)."is good."; ?>

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Count the number of characters and words

count_chars function and str_word_count

<?php 
    $data = "Two Ts and one F.";    foreach (count_chars($data, 1) as $i => $val) {       echo "There were $val instance(s) of \"" , chr($i) , "\" in the string.\n";
    }    echo "<hr>";
    $str = "Hello fri3nd, you're looking good today!";

    print_r(str_word_count($str, 1)); ?>

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查找替换截取

strpos函数、str_replace函数、substr_replace函数、substr函数、strstr函数

<?php 
    $substr = "index.html";
    $log = <<< logfile    192.168.1.11:/www/htdocs/index.html:[2016/08/10:21:58:27]    192.168.1.11:/www/htdocs/index.html:[2016/08/18:01:51:37]    192.168.1.11:/www/htdocs/index.html:[2016/08/20:11:48:27]
logfile;

    $pos =strpos($log, $substr);
    $pos2=strpos($log,"\n",$pos);
    $pos=$pos+strlen($substr)+1;
    $timestamp=substr($log,$pos,$pos2-$pos);
    echo "The file $substr was first accessed on:$timestamp";
    echo "<br>";
    $author="lester@example.com";
    $author=str_replace("@", "at", $author);
    echo "connect the author of this article at $author";
    echo "<br>";
    echo ltrim(strstr($author,"@"), "@");

 ?>

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大小写处理

strtolower函数、strtoupper函数、ucfirst函数、ucwords函数

<?php 
    $url="http://WWWW.BAIDU.COM";    echo strtolower($url),'<br>';
    $str="hello world";    echo strtoupper($str),'<br>';
    $str="php is the most popular language ";    echo ucfirst($str),'<br>';    echo ucwords($str); ?>

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