Chapter 4 Data Processing-PHP String Processing-Zheng Aqi (continued)_PHP Tutorial

1.字符串的定义与显示
定义:通过””,''来标志
显示:echo()和print(),但print()具有返回值值，1，而echo()没有，但echo比print()要快，print()能用在复合语句中。
2.字符串的格式化
printf(string $format[,mixed$args])
第一参数是格式字符串，$args是要替换进来的值，prinf(“%d”,$num);
说明，如果想打印一个”%”，必须用”%”,浮点数f,八进制用”0”
3.常用的字符串函数
1.计算字符串的长度
strlen(string $string),说明，1个英文长度1个字符，1个汉字长度为2个字符，空格也算一个字符。
2.将字符串改变大小写
转为小写：strtolower()
转为大写：strtoupper()
将第一个字符大写: ucfirst()
将每个单词的第一个字母大写 ucwords()
3.字符串裁剪。
当一个字符串的首尾有多余的空白字符，如空格、制表符等可以用
string trim(string $str[,string $charlist])
string rtrim(string $str[sring $charlist])
string itrim(string $str[,string $charlist])
表4.1 trim、itrim、rtrim函数的默认删除字符

字 符	ASCII码	意 义
" "	32(0x20)	空格
"\t"	9(0x09)	制表符
"\n"	10(0x)	换行
"\r"	13(0x0D)	回车
"\0"	0(0x00)	空字节
"\x0B"	11(0x0B)	垂直制表符

4. Searching for strings
string strstr(string $a, string $b)
Explanation: The strstr() function is used to find the position where the string pointer $b appears in the string $a.
And returns the string starting from $b to the end of $a string in $a string.
If there is no return value, that is, $b is not found, then FALSE is returned. The strstr() function also has a function of the same name, strchr().
5. Strings and ASCII codes
4. Comparison of strings
The comparison functions include
strcmp() //case sensitive
strcasecmp()// Insensitive to case
strncmp() //Comparison part
strncasecmp()//Insensitive to case, comparison part
5. String replacement
str_replace(search ,replace,subject)
Instructions to use the new string replace to replace the search string in the string subject
$str="I love you";
$replace=" lucy";
$end=str_replace("you",$replace,$str);
echo $end; //Output "I love lucy"
?>
is case sensitive , many-to-one and many-to-many replacements can also be achieved, but one-to-many replacement cannot be achieved.
$str="What Is Your Name";
$array=array("a","o","A","O","e");
echo str_replace($array, "",$str); //Many-to-one replacement, output "Wht Is Yur Nm"
$array1=array("a","b","c") ;
$array2=array("d","e","f");
echo str_replace($array1,$array2, "abcdef"); //Many-to-many replacement, output "defdef "
?>
substr_replace
Replace part of the string.
6. Strings and HTML
Abbreviated
7. Other string functions
1. Strings and arrays
a. Convert strings to arrays
The explode() function can split another string with the specified string and return an array
$str="Use spaces to split the string";
array=explode(" " , $str);
pint_r($array);
Output Array ( [0] => use [1] => space [2] => split [3] => string)
?>
b. Convert array to string
implode(string $glue,array $pieces)
$pieces is an array to save the string to be connected, $glue is used for connection String concatenation character. For example:
$array=array("hello","how","are","you");
$str=implode(",",$array); //Use commas as connectors
echo $str; //Output "hello,how,are,you"
?>
c. String encryption function
md5(); crypt (), but once this function is encrypted, it cannot be converted to its original form.
4.3 Example Guestbook Content Processing
A guestbook with email addresses and user messages. To extract the customer's email address and messages, it is required that the email address cannot be preceded by a "." or a comma" before the @ symbol. ,".
Set the content before the @ symbol in the email address as the user's username, and change the first person "I" in the user's message to "I".

Copy code The code is as follows:

Your email address:



Your message:

if(isset($_POST ['bt1']))
{
$Email=$_POST['Email']; //Receive Eamil address
$note=$_POST['note']; //Receive message
if(!$Email||!$note) //Determine whether the value is obtained
echo "<script>alert('Please fill in the email address and message completely!')</script>";
else
{
$array=explode("@", $Email); //Split the email address
if(count($array)!=2) //If there are two @ symbols, an error will be reported
echo "<script>alert('Email address format error!')</script>";
else
{
$username=$array[0]; //Get @ Content before the symbol
$netname=$array[1]; //Get the content after the @ symbol
//If username contains "." or "," an error will be reported
if(strstr($ username,".") or strstr($username,","))
echo "<script>alert('Email address format is wrong! ')</script>";
else
{
$str1= htmlspecialchars("<"); //Output symbol "<"
$str2= htmlspecialchars("> "); //Output the symbol ">"
//Replace "I" in the message with "I"
$newnote=str_replace("I","I",$note);
echo "";
echo "User". $str1. $username . $str2. "Hello! ";
echo "You are". $ netname. "Netizen!
";
echo "
Your message is:
".$newnote."
";
echo "}
}
}
}
?>

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