Detailed explanation of PHP's built-in string processing functions

Characteristics of strings

1. Other types of data used in string type processing functions will automatically be converted into strings and processed

";  //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

";
//但是为了区分数组我们常用下面一种
echo $str{2}."
";
?>

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

";
echo strlen(ltrim($str))."
";
echo strlen(rtrim($str))."
";
echo strlen(trim($str))."
";
 
$str1="123This is Test";
 
//第二个参数指定要删除的字符（串）
echo ltrim($str1,'1')."
";
//删除所有的数字  0..9表示范围
echo ltrim($str1,'0..9')."
";
?>

Add string

str_pad(); Add string (added on the right by default)

";
//两边补充
echo str_pad($str,10,"@",STR_PAD_BOTH)."
";
//从左边补充
echo str_pad($str,10,"@",STR_PAD_LEFT)."
";
?>

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

";
echo strtolower($str)."
";
echo ucfirst($str)."
";
echo ucwords($str)."
";
?>

String formatting related to HTML tags

nl2br(); The function inserts an HTML newline character (< before each new line (\n) in the string) br />).

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 '
< ( Less than) becomes< Add a backslash before the specified predefined characters:

  input:
     
     


 
 
";
//函数把字符转换为 HTML 实体。
echo htmlentities($_GET["str"],ENT_NOQUOTES)."
";
//函数把一些预定义的字符转换为 HTML 实体。
echo htmlspecialchars($_GET["str"])."
";
//去掉由addslashes()函数加的 \
echo stripslashes($_GET["str"])."
";
//结合使用
echo htmlentities(stripslashes($_GET["str"]))."
";
 
 
// 函数剥去 HTML、XML 以及 PHP 的标签。
echo strip_tags($_GET["str"])."
";
?>

";
echo number_format($a)."
";
//小数点保留三位，千分位用“,”隔开，小数点用“.”
echo number_format($a,3,'.',',')."
";
?>

";
echo strrev($str)."
";
?>

md5_file();

The function calculates the MD5 hash of the file.

The md5() function uses RSA data security, including the MD5 message digest algorithm.

0){
  echo '$str1>$str2';
}else{
  echo '$str1<$str2';
}
?>

The above detailed explanation of PHP’s built-in string processing functions is all the content shared by the editor. , I hope it can give everyone a reference, and I also hope everyone will support the PHP Chinese website.

For more detailed explanations of PHP’s built-in string processing functions, please pay attention to the PHP Chinese website!