php security field and to prevent cross-site scripting XSS filter function

function escape($string) {
    global $_POST;
    $search = array (
        '/</i',
        '/>/i',
        '/\">/i',
        '/\bunion\b/i',
        '/load_file(\s*(\/\*.*\*\/)?\s*)+\(/i',
        '/into(\s*(\/\*.*\*\/)?\s*)+outfile/i',
        '/\bor\b/i',
        '/\<([\/]?)script([^\>]*?)\>/si',
        '/\<([\/]?)iframe([^\>]*?)\>/si',
        '/\<([\/]?)frame([^\>]*?)\>/si'
    );
    $replace = array (
        '<',
        '>',
        '">',
        'union ',
        'load_file  (',
        'into  outfile',
        'or ',
        '<\\1script\\2>',
        '<\\1iframe\\2>',
        '<\\1frame\\2>'
    );
    if (is_array ( $string )) {
        $key = array_keys ( $string );
        $size = sizeof ( $key );
        for($i = 0; $i < $size; $i ++) {
            $string [$key [$i]] = escape ( $string [$key [$i]] );
        }
    } else {
        if (! $_POST ['stats_code'] && ! $_POST ['ad_type_code_content']) {
            $string = str_replace ( array (
                '\n',
                '\r'
            ), array (
                chr ( 10 ),
                chr ( 13 )
            ), preg_replace ( $search, $replace, $string ) );
            $string = remove_xss ( $string );
        } else {
            $string = $string;
        }
    }
    return $string;
}
 
function remove_xss($val) {
    $val = preg_replace ( '/([\x00-\x08\x0b-\x0c\x0e-\x19])/', '', $val );
 
    $search = 'abcdefghijklmnopqrstuvwxyz';
    $search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $search .= '1234567890!@#$%^&*()';
    $search .= '~`";:?+/={}[]-_|\'\\';
    for($i = 0; $i < strlen ( $search ); $i ++) {
 
        $val = preg_replace ( '/(&#[xX]0{0,8}' . dechex ( ord ( $search [$i] ) ) . ';?)/i', $search [$i], $val );
 
        $val = preg_replace ( '/(�{0,8}' . ord ( $search [$i] ) . ';?)/', $search [$i], $val );
    }
 
    $ra1 = array (
        'javascript',
        'vbscript',
        'expression',
        'applet',
        'meta',
        'xml',
        'blink',
        'script',
        'object',
        'iframe',
        'frame',
        'frameset',
        'ilayer',
        'bgsound'
    );
    $ra2 = array (
        'onabort',
        'onactivate',
        'onafterprint',
        'onafterupdate',
        'onbeforeactivate',
        'onbeforecopy',
        'onbeforecut',
        'onbeforedeactivate',
        'onbeforeeditfocus',
        'onbeforepaste',
        'onbeforeprint',
        'onbeforeunload',
        'onbeforeupdate',
        'onblur',
        'onbounce',
        'oncellchange',
        'onchange',
        'onclick',
        'oncontextmenu',
        'oncontrolselect',
        'oncopy',
        'oncut',
        'ondataavailable',
        'ondatasetchanged',
        'ondatasetcomplete',
        'ondblclick',
        'ondeactivate',
        'ondrag',
        'ondragend',
        'ondragenter',
        'ondragleave',
        'ondragover',
        'ondragstart',
        'ondrop',
        'onerror',
        'onerrorupdate',
        'onfilterchange',
        'onfinish',
        'onfocus',
        'onfocusin',
        'onfocusout',
        'onhelp',
        'onkeydown',
        'onkeypress',
        'onkeyup',
        'onlayoutcomplete',
        'onload',
        'onlosecapture',
        'onmousedown',
        'onmouseenter',
        'onmouseleave',
        'onmousemove',
        'onmouseout',
        'onmouseover',
        'onmouseup',
        'onmousewheel',
        'onmove',
        'onmoveend',
        'onmovestart',
        'onpaste',
        'onpropertychange',
        'onreadystatechange',
        'onreset',
        'onresize',
        'onresizeend',
        'onresizestart',
        'onrowenter',
        'onrowexit',
        'onrowsdelete',
        'onrowsinserted',
        'onscroll',
        'onselect',
        'onselectionchange',
        'onselectstart',
        'onstart',
        'onstop',
        'onsubmit',
        'onunload'
    );
    $ra = array_merge ( $ra1, $ra2 );
 
    $found = true;
    while ( $found == true ) {
        $val_before = $val;
        for($i = 0; $i < sizeof ( $ra ); $i ++) {
            $pattern = '/';
            for($j = 0; $j < strlen ( $ra [$i] ); $j ++) {
                if ($j > 0) {
                    $pattern .= '(';
                    $pattern .= '(&#[xX]0{0,8}([9ab]);)';
                    $pattern .= '|';
                    $pattern .= '|(�{0,8}([9|10|13]);)';
                    $pattern .= ')*';
                }
                $pattern .= $ra [$i] [$j];
            }
            $pattern .= '/i';
            $replacement = substr ( $ra [$i], 0, 2 ) . ' ' . substr ( $ra [$i], 2 );
            $val = preg_replace ( $pattern, $replacement, $val );
            if ($val_before == $val) {
 
                $found = false;
            }
        }
    }
    return $val;
}