如何在PHP中打印彩色字符串

Question

我想用这种颜色打印一个字符串：

1. 黄色，当char是奇数时;
2. 蓝色，当char是偶数时;
3. red，当char是元音时;
4. 绿色，char是辅音;

例如：$string = "hi12";

1. h =绿色
2. i = red
3. 1 =黄色
4. 2 =蓝色

我已经尝试过这个但似乎不起作用：

$string = "hi12"; <br>
$strCol = ""; <br>
$char = ""; <br>
$color = ""; <br>

for($i = 0; $i < strlen($string); $i++){
    $char = $string[$i];   
    if(is_numeric($char)){
        if(($char % 2) == 1){
            $color = "<p style='color:yellow;'>" + $char + "</p>";
            $strCol .= $color;
        }
        else if(($char % 2) == 0){
            $color = "<p style='color:blue;'>" + $char + "</p>";
            $strCol .= $color;
        }
    }
    else{
        if(preg_match('/^[aeiou]/i', $char)){
            $color = "<p style='color:red;'>" + $char + "</p>";
            $strCol .= $color;
        }
        else{
            $color = "<p style='color:green;'>" + $char + "</p>";
            $strCol .= $color;
        }
    }
} 

echo $strCol;

Answer 1

$isGreen = false;
$isRed = false;
$isYellow = false;
$isBlue = false;

$string = 'some text with space';
$letterCount = strlen($string) - substr_count($string, ' ');
if (0 == $letterCount % 4) {
    $isBlue = true;
} elseif (1 == $letterCount % 4) {
    $isGreen = true;
} elseif (2 == $letterCount % 4) {
    $isRed = true;
} else {
    $isYellow = true;
}

for ($i = strlen($string) - 1; $i >= 0; $i--) {
    $letter = substr($string, $i, 1);

    if (' ' == $letter) {
        continue;
    }

    if ($isGreen) {
        $colour = 'green';
        $isGreen = !$isGreen;
        $isBlue = !$isBlue;
    } elseif ($isRed) {
        $colour = 'red';
        $isGreen = !$isGreen;
        $isRed = !$isRed;
    } elseif ($isYellow) {
        $colour = 'yellow';
        $isRed = !$isRed;
        $isYellow = !$isYellow;
    } else {
        $colour = 'blue';
        $isBlue = !$isBlue;
        $isYellow = !$isYellow;
    }
    $string = substr_replace($string, sprintf('<span style="color:%s">%s</span>', $colour, $letter) , $i, 1);
}

echo $string;