PHP code for filtering arrays by first character

$array = array(
'abcd',
'abcde',
'bcde',
'cdef',
'defg',
'defgh'
 );
$str = '~'.implode('~',$array).'~';
$word = $_GET['word']; //url = xxx.php?word=a
preg_match_all( "/~({$word}(?:[^~]*))/i",$str,$matches);
var_dump($matches[1]);
/ /output
//array(2) { [0]=> string(4) "abcd" [1]=> string(5) "abcde" }
//End_php
?>

Instructions: There is a problem when using the above code: there will be problems when using ',' (comma) as the delimiter. Please be careful when using it.