PHP returns the string function addslashes() that adds a backslash before the specified character.

1. addslashes() function

1. The addslashes() function adds a backslash before the specified predetermined character. Syntax: addslashes(str);

2. The parameter is a string

3. There are four kinds of predefined characters: single quotation mark ('), double quotation mark ("), Backslash (\) and NULL

4. For example:

  <?php
    $str="Who&#39;s John Adams?";    echo $str."This is not safe in a database query.<br/>";//输出：Who&#39;s John Adams?This is not safe in a database query.
    echo addslashes($str)."This is safe in a database query.";//输出：Who\&#39;s John Adams?This is sage in a database query.
   ?>

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2. addcslashes() function

1.addcslashes () function adds a backslash before the specified character.

Syntax: addcslashes(str,chararcters);

2. The parameter str is required and specifies the character to be checked. String, and character is optional, specifying the characters or character range affected by addcslashes()

3. Example 1:

<?php
    $str="Hello,my name is John Adams.";
    echo $str;   //输出：Hello,my name is John Adams.echo addcslashes($str,&#39;m&#39;);  //输出：
    Hello,\my na\me is John Ada\ms.echo addcslashes($str,&#39;J&#39;);  //输出：Hello,my name is \John Adams
  ?>

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Example. 2.

<?php$str="Hello,my name is John Adams.";
echo $str;  //输出：Hello,my name is John Adams.
echo addcslashes($str,&#39;A..Z&#39;);  //输出：\Hello,my name is \John \Adams.
echo addcslashes($str,&#39;a..z&#39;);  //输出：H\e\l\l\o,\m\y \n\a\m\e \i\s J\o\h\n A\d\a\m\s.
echo addcslashes($str,&#39;a..h&#39;);  //输出：H\ello,my n\am\e is Jo\hn A\d\ams.
?>

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Note: The addcslashes() function is case-sensitive for the specified character or character range

in the character ". Add a backslash before W":

<?php 
$str = addcslashes("Hello World!","W");
echo($str); 
?>

Definition and usage

addcslashes() function returns a string with a backslash before the specified character.

Comment: The addcslashes() function is case-sensitive.

Comments: 0 (NULL), r (carriage return), n (line feed), t (form feed), f (tab character). ) and v (vertical tab) be careful when applying addcslashes(). In PHP, \0, \r, \n, \t, \f and \v are predefined escape sequences

addcslashes(string,characters)

Description

Return value:

<?php
$str = "Welcome to my humble Homepage!";
echo $str."<br>";
echo addcslashes($str,&#39;m&#39;)."<br>";
echo addcslashes($str,&#39;H&#39;)."<br>";
?>

<?php
$str = "Welcome to my humble Homepage!";
echo $str."<br>";
echo addcslashes($str,&#39;A..Z&#39;)."<br>";
echo addcslashes($str,&#39;a..z&#39;)."<br>";
echo addcslashes($str,&#39;a..g&#39;);
?>

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