php删除字符串的空格

$test = " abc";
//方法一：函数把 HTML 实体转换为字符。
$converted = html_entity_decode($test),chr(0xc2).chr(0xa0);  
//方法二：
$converted = strtr($myHTML, array_flip(get_html_translation_table(HTML_ENTITIES, ENT_QUOTES))); 
//php:45:string ' abc' (length=5) 
$converted = trim($converted,chr(0xC2).chr(0xA0)); // should work
var_dump($converted);

$str = ' t e  s t';
$str = preg_replace('/\s+/', '', $str);
// 将会改变为'test'

$str = " t e  s t";
$str=str_replace(" ",'',$str);
echo $str