Check if a string contains a certain number

Question

I have a string

8,7,13,14,16

Whats the easiest way to determine if a given number is present in that string?

$numberA = "13";
$string = "8,7,13,14,16";

if($string magic $numberA){
$result = "Yeah, that number is in there";
} else {
$result = "Sorry.";
}

Looking for magic.

Answer 1

<?php 
in_array('13', explode(',', '8,7,13,14,16'));
?>

…will return whether '13' is in the string.

Just to elaborate: explode turns the string into an array, splitting it at each ',' in this case. Then, in_array checks if the string '13' is in the resulting array somewhere.

Answer 2

if (strpos(','.$string.',' , ','.$numberA.',') !== FALSE) {
    //found
}

Notice guard ',' chars, they will help to deal with '13' magic '1, 2, 133' case.

Answer 3

A simple string search should do if you are just checking to find existence of the string. I dont speak php but i think this is how it could be done.

$mystring = '8,7,13,14,16';
$findme   = '13';

if (preg_match('/(?>(^|[^0-9])'.$findme.'([^0-9]|$))/', $mystring)) {
    $result = "Yeah, that number is in there";
} else {
    $result = "Sorry.";
}

Answer 4

Another way, that might be more efficient for laaaaaaaarge strings, is using a regexp:

$numberA = "13";
$string = "8,7,13,14,16";

if(preg_match('/(^|,)'.$numberA.'($|,)/', $string)){
    $result = "Yeah, that number is in there";
} else {
    $result = "Sorry.";
}

Answer 5

Make sure you match the full number in the string, not just part of it.

function numberInList($num, $list) {
    return preg_match("/\b$num\b/", $list);
}
$string = "8,7,13,14,16";    
numberInList(13, $string); # returns 1
numberInList(8, $string); # returns 1
numberInList(1, $string); # returns 0
numberInList(3, $string); # returns 0