php常用字符串函數小結

php內置了98個字符串函數（除了基於正則表達式的函數，正則表達式在此不在討論范圍），能夠處理字符串中能遇到的每一個方面內容，本文對常用字符串函數進行簡單的小結，主要包含以下8部分：1.確定字符串長度、2.比較字符串、3.分割連接反轉、4.html與字符串相互轉化、5.填充和剔除字符串、6.統計字符和單詞個數、7.查找替換截取、8.大小寫處理。

確定字符串長度

strlen函數和mb_strlen函數，后者需要開啟mbstring擴展

<?php 
    header('content-type:text/html;charset=utf-8');
    $str = 'abcdef';
    echo strlen($str); // 6
    echo "<br/>";
    $str = ' ab cd ';
    echo mb_strlen($str); // 7
    echo "<br/>";
    //strlen 是計算字符串"字節"長度 
    //mb_strlen,是根據編碼,計算字符串的"字符"個數. 

    $str='中華人民共和國';
    echo "字節長度是".strlen($str);//在 UTF-8編碼下，一個漢字占3個字節 在gbk中一個漢字占2個字節
    echo "<br/>";
    echo "字符長度是".mb_strlen($str,'utf-8');
 ?>

比較字符串

strcmp函數、strcasecmp函數、strspn函數、strcspn函數

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

	$email1="www.baidu.com";
	$email2="WWW.BAIDU.COM";
	//不區分大小寫
	if (!strcasecmp($email1, $email2)) {
		echo "ok",'<br>';
	}
	//求兩個字符串相同的部分
	$password="1233345";
	if (strspn($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";
	}
	
 ?>

分割連接反轉

str_split函數、split函數、explode函數和implode函數

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

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

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

	$str = 'abc,中國,美國,日本'; 
	// explode,是根據指定的分割符,把字符串拆成數組. 
	$arr = explode(',',$str); 
	print_r($arr); 
	// implode,是根據指定的連接符,把數組再拼接成字符串 
	$arr = explode(',',$str); 
	echo implode('~',$arr),'<br />'; 
	// 你可以只傳一個數組做參數,不指定連接符, 
	// 這樣,將把數組單元直接拼接起來 
	echo implode($arr);

 ?>

html與字符串相互轉化

htmlspecialchars函數、strip_tags函數、get_html_translation_table函數和addcslashes函數和htmlentities函數

<?php 

	$str = "hello ', world"; 
	echo $str,'<br />';
	echo $str= addslashes($str),'<br />';
	echo stripslashes($str),'<br />';
	$str = '<ab>'; 
	echo $str,'<br />'; 
	echo htmlspecialchars($str); 
	echo "</br>";
	$str="Email <a href='[e-mail]'>[e-mail]</a>";
	echo strip_tags($str);

 ?>

填充和剔除字符串

trim函數、ltrim函數、rtrim函數、str_pad函數、chunk_split函數

<?php 
	$str = '12345678'; 
	echo chunk_split($str,3,',');
	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.";
 ?>

統計字符和單詞個數

count_chars函數和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));

 ?>

查找替換截取

strpos函數、str_replace函數、substr_replace函數、substr函數、strstr函數

<?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="[e-mail]";
    $author=str_replace("@", "at", $author);
    echo "connect the author of this article at $author";
    echo "<br>";
    echo ltrim(strstr($author,"@"), "@");

 ?>

大小寫處理

strtolower函數、strtoupper函數、ucfirst函數、ucwords函數

<?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);
 ?>