Input value/form submission parameter filtering effectively prevents SQL injection

Input value form submission parameter filtering can effectively prevent SQL injection or illegal attacks. The following describes some good methods. if you are interested, do not miss the input value/form submission parameter filtering, methods to prevent SQL injection or illegal attacks:
The code is as follows:
/**
* Filter keywords for SQL and PHP file operations
* @ Param string $ string
* @ Return string
* @ Author zyb
*/
Private function filter_keyword ($ string ){
$ Keyword = 'SELECT | insert | update | delete | \ '| \/\ * | \. \. \/| \. \/| union | into | load_file | outfile ';
$ Arr = explode ('|', $ keyword );
$ Result = str_ireplace ($ arr, '', $ string );
Return $ result;
}

/**
* Check whether the entered number is valid. the corresponding id is valid; otherwise, false is returned.
* @ Param integer $ id
* @ Return mixed
* @ Author zyb
*/
Protected function check_id ($ id ){
$ Result = false;
If ($ id! = ''&&! Is_null ($ id )){
$ Var = $ this-> filter_keyword ($ id); // filter keywords for SQL and PHP file operations
If ($ var! = ''&&! Is_null ($ var) & is_numeric ($ var )){
$ Result = intval ($ var );
}
}
Return $ result;
}

/**
* Check whether the entered characters are valid. the corresponding id is valid; otherwise, false is returned.
* @ Param string $ string
* @ Return mixed
* @ Author zyb
*/
Protected function check_str ($ string ){
$ Result = false;
$ Var = $ this-> filter_keyword ($ string); // filter keywords for SQL and PHP file operations
If (! Empty ($ var )){
If (! Get_magic_quotes_gpc () {// determines whether magic_quotes_gpc is enabled.
$ Var = addslashes ($ string); // filter submitted data when magic_quotes_gpc is not enabled
}
// $ Var = str_replace ("_", "\ _", $ var); // filter '_'
$ Var = str_replace ("%", "\ %", $ var); // filter '%'
$ Var = nl2br ($ var); // press enter to convert
$ Var = htmlspecialchars ($ var); // html tag conversion
$ Result = $ var;
}
Return $ result;
}