recherche chaine decaractere

<?php
function ote_accent($str){
$ch = strtr($str,
'ÀÁÂÃÄÅÇÈÉÊËÌÍÎÏÒÓÔÕÖÙÚÛÜÝàáâãäåçèéêëìíîïðòóôõöùúûüýÿ',
'AAAAAACEEEEIIIIOOOOOUUUUYaaaaaaceeeeiiiioooooouuuuyy');
return $ch;
}

function check1($pattern,$Chaine){

  if(preg_match($pattern,$Chaine)){
  return "<strong style='color:green;'>Chaine OK</strong>";
  }else{
  return "<strong style='color:red;'>Chaine NON OK</strong>";
  }

}

// /^[a-z0-9_-]*$/ pcre

if(isset($_POST['tocheck']) && !empty($_POST['tocheck'])){
$chaine=$_POST['tocheck'];
//$chaine=ote_accent($chaine);
echo check1($pattern='/^[a-zA-Z 0-9_-]*$/',$chaine); //+ espace et majuscules
}else{
echo $form = '<form method="post" action="">

test <input type="text" name="tocheck" size=20>
<input type="submit" value="tester">
</form>';

}
?>