Prevent injection attacks in PHP

You can use PHP built-in functions such as addslashes to directly provide functions for ease of use.
Function verifyinput ($ input)
{

If (! Get_magic_quotes_gpc ())
{
// Magic_quotes_gpc is on by default and will automatically escape characters such '.
$ Input = addslashes ($ input );
}

}
In the display mode
<? Echo htmlentities (stripslashes (...)?> Normal display

However, I personally think that it should be judged when the user inputs it. For example, if only numbers and letters are allowed
Enter the 'number and other characters that have other meanings. Of course, if you do need it in some cases, use the above method to filter it.