php删除多余的空格

$str = "  Hello World!  ";
$trimmedStr = trim($str);
echo $trimmedStr; // 输出：Hello World!

$str = "\tHello World!\n";
$trimmedStr = trim($str, "\t\n");
echo $trimmedStr; // 输出：Hello World!

$str = "  Hello World!  ";
$leftTrimmedStr = ltrim($str);
$rightTrimmedStr = rtrim($str);
echo $leftTrimmedStr; // 输出：Hello World!  
echo $rightTrimmedStr; // 输出：  Hello World!

$str = "  Hello   World!  ";
$trimmedStr = preg_replace('/\s+/', ' ', $str);
echo $trimmedStr; // 输出：Hello World!