PHP Basics Tutorial-form validation (required, data retention after submission)

First, several element records used in the form validation

1.htmlspecialchars (), which is used to escape the special characters entered by the user as normal, such as < and > HTML characters are replaced with &lt; and &gt;

2.$_server["Php_self" is a super global variable that returns the current page script name

3.trim () used to remove extra spaces, etc.

4.stripslashes () to remove user-input backslash

Second simple form validation functions

function Test_input ($str) {
	$str = trim ($STR);//Remove whitespace etc
	$str = stripslashes ($STR);//remove backslash from user input
	$str = Htmlspecialchars ($STR);//convert special characters to ordinary characters return
	$str;
}

Prompt code for required items in form

1.php code, verify that the input box is empty, increase the error message for display in HTML, non-null validate and process input

2.HTML code inserts the output error message in the PHP code fragment such as <span class= "error" >*<?php Echo $EMAILERR?></span><br/>

$EMAILERR to save the error message variable, starting with null.

Simple example:

<! DOCTYPE html>  
Show Chart:



Iv. Retention of form data

In the above code, just change the following <input> tags to add php fragment: <input type= ' name= ' value= ' <?php echo $name?> ' >

For <textarea> elements, simply add the PHP fragment between <textarea></textarea>

For radio, more trouble, add code in <input>: <?php if (Isset ($gender)) && $gender = = ' female ') echo ' checked ';? >


<form method= "POST" action= "<?php Echo htmlspecialchars ($_server[' php_self ']);? > "> Name: <input type=" text "name=" name "value=" <?php echo $name;? > > <span class= "error" >*<?php Echo $nameErr?></span><br/> Email: <input type= "Text" Name= "Email" value= "<?php echo $email;? > > <span class= "error" >*<?php echo $emailErr?></span><br/> URL: <input type= "Text" Name= "website" value= "<?php echo $website;? > "><br/> Comments: <textarea name=" Area "rows=" 4 "cols=" "><?php echo $area;? ></textarea><br/> Sex: <input type= "Radio" name= "Gender" <?php if (isset ($gender) && $ gender== "female") echo "checked";? > value= "female" > Female <input type= "Radio" name= "Gender" <?php if (isset ($gender) && $gender = "male") echo "Checked";? > value= "male" > Men <br/> <input type= "Submit" value= "submitted" name= "Submit" ><br/> </form>