Wordpress Deprecated: Invalid characters passed ... these have been ignored Hatası

public static function colourBrightness($hex, $percent) {
// Work out if hash given
$hash = '';
if (stristr($hex,'#')) {
$hex = str_replace('#','',$hex);
$hash = '#';
}
/// HEX TO RGB
$rgb = array(hexdec(substr($hex,0,2)), hexdec(substr($hex,2,2)), hexdec(substr($hex,4,2)));
//// CALCULATE
for ($i=0; $i; $i++) {
// See if brighter or darker
if ($percent > 0) {
// Lighter
$rgb[$i] = round($rgb[$i] * $percent) + round(255 * (1-$percent));
} else {
// Darker
$positivePercent = $percent - ($percent*2);
$rgb[$i] = round($rgb[$i] * $positivePercent) + round(0 * (1-$positivePercent));
}
// In case rounding up causes us to go to 256
if ($rgb[$i] > 255) {
$rgb[$i] = 255;
}
}
//// RBG to Hex
$hex = '';
for($i=0; $i < 3; $i++) {
// Convert the decimal digit to hex
$hexDigit = dechex($rgb[$i]);
// Add a leading zero if necessary
if(strlen($hexDigit) == 1) {
$hexDigit = "0" . $hexDigit;
}
// Append to the hex string
$hex .= $hexDigit;
}
return $hash.$hex;
}