<?php
$pattern = "/^[a-z \-,.:']+$/i";
$subject[] = "I am a test string";
$subject[] = "I am a John O'Connor";
$subject[] = "I am a test with illegal [characters]";
foreach($subject as $s){
if(preg_match($pattern, $s) === 0 ){
echo "string not matched";
} else {
echo "string matched";
}
echo "<br/>";
}
?>