How to sanitize your php input

Never trust user input, it may be malicious, always check your php input.

Check all global arrays like $_GET, $_POST, $_REQUEST, $_COOKIE, allow only known variables and make sure that they contain the right type of data.

What does this mean ? It means that if you have a $_GET[‘id’] variable in your script which has to be an integer, always check it and make sure it is an integer.

Also don’t allow other variables in $_GET or other globals, keep only variables that your scripts need. So, if your script only uses only one variable $_GET[‘id’] then dispose other variables. Here is how I do it.

http://www.codeassembly.com/How-to-sanitize-your-php-input/

cdl_capture_2011-03-05-38_ 000

 

This is $_GET contents


Array

(

    [id] => blabla77

    [name] => John

    [variable1] => somedata

    [variable2] => somedata

)

This is the sanitize code


//in this example script I use two variables, one integer and one string

sanitize($_GET, array( 'id'=>'int', 'name' => 'str') );

This is $_GET contents after sanitization


Array

(

    [id] => 77

    [name] => John

)

We removed unwanted variables and we made sure that every variable has the correct data type.

Here is the class that I use for santiziation, feel free to improve it to suit your needs.


/*

    Sanitize class

    Copyright (C) 2007 CodeAssembly.com 



    This program is free software: you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by

    the Free Software Foundation, either version 3 of the License, or

    (at your option) any later version.



    This program is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of

    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    GNU General Public License for more details.



    You should have received a copy of the GNU General Public License

    along with this program.  If not, see http://www.gnu.org/licenses/

*/

/**

* Sanitize only one variable .

* Returns the variable sanitized according to the desired type or true/false

* for certain data types if the variable does not correspond to the given data type.

*

* NOTE: True/False is returned only for telephone, pin, id_card data types

*

* @param mixed The variable itself

* @param string A string containing the desired variable type

* @return The sanitized variable or true/false

*/



function sanitizeOne($var, $type)

{      

        switch ( $type ) {

                        case 'int': // integer

                        $var = (int) $var;

                        break;



                        case 'str': // trim string

                        $var = trim ( $var );

                        break;



                        case 'nohtml': // trim string, no HTML allowed

                        $var = htmlentities ( trim ( $var ), ENT_QUOTES );

                        break;

                       

                        case 'plain': // trim string, no HTML allowed, plain text

                        $var =  htmlentities ( trim ( $var ) , ENT_NOQUOTES )  ;

                        break;



                        case 'upper_word': // trim string, upper case words

                        $var = ucwords ( strtolower ( trim ( $var ) ) );

                        break;



                        case 'ucfirst': // trim string, upper case first word

                        $var = ucfirst ( strtolower ( trim ( $var ) ) );

                        break;



                        case 'lower': // trim string, lower case words

                        $var = strtolower ( trim ( $var ) );

                        break;



                        case 'urle': // trim string, url encoded

                        $var = urlencode ( trim ( $var ) );

                        break;



                        case 'trim_urle': // trim string, url decoded

                        $var = urldecode ( trim ( $var ) );

                        break;

                       

                        case 'telephone': // True/False for a telephone number

                        $size = strlen ($var) ;

                        for ($x=0;$x<$size;$x++)

                        {

                                if ( ! ( ( ctype_digit($var[$x] ) || ($var[$x]=='+') || ($var[$x]=='*') || ($var[$x]=='p')) ) )

                                {

                                        return false;

                                }

                        }

                        return true;

                        break;

                       

                        case 'pin': // True/False for a PIN

                        if ( (strlen($var) != 13) || (ctype_digit($var)!=true) )

                        {

                                return false;

                        }

                        return true;

                        break;

                       

                        case 'id_card': // True/False for an ID CARD

                        if ( (ctype_alpha( substr( $var , 0 , 2) ) != true ) || (ctype_digit( substr( $var , 2 , 6) ) != true ) || ( strlen($var) != 8))

                        {

                                return false;

                        }

                        return true;

                        break;

                       

                        case 'sql': // True/False if the given string is SQL injection safe

                        //  insert code here, I usually use ADODB -> qstr() but depending on your needs you can use mysql_real_escape();

                        return mysql_real_escape_string($var);

                        break;

                }      

        return $var;

       

}





/**

* Sanitize an array.

*

* sanitize($_POST, array('id'=>'int', 'name' => 'str'));

* sanitize($customArray, array('id'=>'int', 'name' => 'str'));

*

* @param array $data

* @param array $whatToKeep

*/



function sanitize( &$data, $whatToKeep )

{

        $data = array_intersect_key( $data, $whatToKeep );

       

        foreach ($data as $key => $value)

        {

                $data[$key] = sanitizeOne( $data[$key] , $whatToKeep[$key] );

        }

}

You can also use php filter to implement your sanitization code, just add new data types to the above class using php filter.

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