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Characteristics of strings
1. Other types of data used in string type processing functions will automatically be converted into strings and processed
<?php echo substr("abcdefghijklmn",2,4),"<br>"; //cdef //使用数字会自动转化为字符串 echo substr(123456,2,4); //3456 ?>
2. Yes Treat strings as arrays and character sets
<?php $str="abcdefg"; //下面这两种方法都可以输出想要的字符 echo $str[2]."<br>"; //但是为了区分数组我们常用下面一种 echo $str{2}."<br>"; ?>
Powerful built-in string processing functions
1. Commonly used string output functions
echo()
print()
die()----exit()
printf() Format string
sprintf() Return formatted string
2. Commonly used String formatting function
Remove characters
ltrim(); Remove the string on the left (spaces are removed by default)
rtrim(); Remove the string on the right
trim(); Remove the strings on both sides
<?php $str=" abc "; echo strlen($str)."<br>"; echo strlen(ltrim($str))."<br>"; echo strlen(rtrim($str))."<br>"; echo strlen(trim($str))."<br>"; $str1="123This is Test"; //第二个参数指定要删除的字符(串) echo ltrim($str1,'1')."<br>"; //删除所有的数字 0..9表示范围 echo ltrim($str1,'0..9')."<br>"; ?>
Add string
str_pad(); Add string (added on the right by default)
<?php $str="hello"; //默认从右边补充 echo str_pad($str,10,"@")."<br>"; //两边补充 echo str_pad($str,10,"@",STR_PAD_BOTH)."<br>"; //从左边补充 echo str_pad($str,10,"@",STR_PAD_LEFT)."<br>"; ?>
Case conversion
strtolower(); All characters are converted to lowercase
strtoupper(); All characters are converted to uppercase
ucfirst(); The first letter of each word is converted to uppercase
ucword(); The first letter of each word is converted Into uppercase
<?php $str="My name is TOM!"; echo strtoupper($str)."<br>"; echo strtolower($str)."<br>"; echo ucfirst($str)."<br>"; echo ucwords($str)."<br>"; ?>
String formatting related to HTML tags
nl2br(); The function inserts an HTML newline character (65e199e482cf6f44f7f2441f7a10f472).
htmlentities(); Function converts characters into HTML entities.
htmllspeciachars(); The function converts some predefined characters into HTML entities.
The predefined characters are:
& (ampersand) becomes &
"" (double quote) becomes "
'' (single quote) becomes '
1c5c63ed842c46e2468a1261bea229410 - if string1 is greater than string2
<?php $str1="abcd"; $str2="abcd"; if(strcmp($str1,$str2)==0){ echo '$str1=$str2'; }elseif(strcmp(str1,$str2)>0){ echo '$str1>$str2'; }else{ echo '$str1<$str2'; } ?>
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