php 去掉字符串中的空格

<?php
//删除所有空格
echo str_replace(' ', '', ' a bab ');echo "
";
echo preg_replace('/ /', '', ' ab ab ');echo "
";
echo strtr(' ab ab ', array(' '=>''));echo "
";
function trimall($str)//删除所有的空格
{
 $qian=array(" ","　","	","
","
");
 $hou=array("","","","","");
 return str_replace($qian,$hou,$str); 
}
echo trimall(" a v ");
echo "
";
?>