Check if part of a string is a number - php

Question

Im building an API which can read messages from a SQL database. I check the URL with the following if statement: if ($uri[0] == "/rooms/1/messages"). The 1 is the room number requested, but there are more rooms than "1".
What I want is an if statement like this: if ($uri[0] == "/rooms/" . $thisHasToBeANumber . "/messages")
I have thought about exploding the URL on the "/" but I dont know from the beginning how much slashes there are in the URL.
My whole function:
function checkUrl()
{
// Variables about URL, first explode with "api" then with "?"
$uri = explode('api', $_SERVER['REQUEST_URI']);
$uri = explode('?', $uri[1]);
// Check the url path for "/rooms/1/messages/" and check request method
if ($uri[0] == "/rooms/ " . $thisHasToBeANumber . "/messages") {
if ($_SERVER["REQUEST_METHOD"] === "GET") {
$roomId = explode('/', $uri[0])[2];
getMessages($roomId);
} else {
header("HTTP/1.0 400");
die("Wrong request method");
}
}
// Check the url path for "/messages/" and check request method
elseif ($uri[0] == "/messages") {
if ($_SERVER["REQUEST_METHOD"] === "POST") {
// Get POST parameters
$inputJSON = file_get_contents('php://input');
$input = json_decode($inputJSON, TRUE);
if (!empty($input['content']) && !empty($input['roomId'])) {
$messageContent = $input['content'];
$roomId = $input['roomId'];
$userId = getUserId($_GET['token']);
sendMessage($userId, $messageContent, $roomId);
} else {
header("HTTP/1.0 400");
die("Missing arguments");
}
} else {
header("HTTP/1.0 400");
die("Wrong request method");
}
}
// Check the url path for "/rooms/" and check request method
elseif ($uri[0] == "/rooms") {
if ($_SERVER["REQUEST_METHOD"] === "GET") {
getRoomNames();
} else {
header("HTTP/1.0 400");
die("Wrong request method");
}
}
// Path is not found
else {
header("HTTP/1.0 404");
die("Path not found");
}
}```

Answer 1

I think you are looking for regular expressions.
And preg_match ( documentation ) is the thing you are looking for.
If we do something like this:
if ( ( preg_match( "rooms/([\d]+)/messages", $uri[0], $match ) === 1 ) {
if ($_SERVER["REQUEST_METHOD"] === "GET") {
//$roomId = match[1];
getMessages($match[1]);
} else {
header("HTTP/1.0 400");
die("Wrong request method");
}
}
!Note
The reason why we use preg_match( ... ) === 1 is because of the return value.

Answer 2

I don't know exactly what kind of data you will receive, but it looks like you can use a regular expression. For example, assume that $uri is the string and you want a number in the format: "/room/NUMBER/messages". You can use:
preg_match("~/room/([0-9]+)/messages~", $uri, $matches);
If the pattern fits, $matches[1] will contain the room number.
You can put this into an if-else with:
if(isset($matches[1])) {
$roomnumber = $matches[1];
// do what you want
} else {
// There is no room number
}

Answer 3

I would expect the URL to always come in the same format, so using explode should be safe. You would need to work out what the format was and then extract the number from the right position.
Alternatively, you could use RegEx. That will allow you to be more flexible in extracting the room number. Some example code you could use would be:
$uri = '/room/123/abc'; // test code
if (preg_match('/(^|\/)room\/(\d+)($|\/)/', $test, $matches)===1) {
$roomId = $matches[2];
} else {
// no match
}
To explain, preg_match will take a RegEx pattern and apply it to the URL and return an array of matches. The RegEx in the example will look for the sequence "room/" following a slash or at the beginning of your URL and then followed by one or more numerical digits (which are returned in the array) and finally by either another slash or the end of the string. The numerical digits are returned as the third match.