Check with jquery if result/echo from PHP starts with "abc" - php

Question

I am using jquery and ajax to submit forms without page reloading and then depending on the result (whether it is a success or an error) I print the message in two different divs. Since success and error in ajax only checks the client/server connection I echo some stuff from PHP when query succeeds and depending on that I condition what to do with the message. Jquery/ajax part looks like that (normally I use two different divs, but to simplify the example I will use alerts):
success: function (result) {
if (result == 'success') {
alert("Success!");
} else {
alert("There was an error.");
}
},
This works perfectly, but I would like to improve its usability.
Now the question is: can I use in if (result == part something like str.match? For example if there were some problems running the query I would echo in php echo "Error: >error description here<"; Could I then somehow use str.match(/^Error/) in my if condition and echo the entire message?

Answer 1

Don't use string matching for this task. Use HTTP response codes - that's what they're there for! The http_response_code function in PHP is designed for this exact purpose:
<?php
if ( /* error condition */ ) {
http_response_code(400); // "Bad request" response code
echo 'Invalid parameters';
}
else {
echo 'Success'; // response code is 200 (OK) by default
}
Then you can use jQuery's done and fail callbacks to handle the two cases separately:
$.ajax(url, params)
.done(function(response) { alert('all good: ' + response); })
.fail(function(response) { alert('error: ' + response); })

Answer 2

To check if the message starts with Error: you can use indexOf:
if (result.indexOf('Error:') === 0) {
// Starts with `Error:`
}
indexOf will return the index starting from 0 where Error: is found in the result string.
Reference: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf
The indexOf() method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex. Returns -1 if the value is not found.

Answer 3

to answer the 'improve' part of your question i would do some JSON.
php:
//Your code here and create an associative array like so:
if($errors){
$data(
'results'=>'errors',
'message'=>'it failed'
);
}else{
$data(
'results'=>'success',
'message'=>'it worked'
);
}
echo json_encode($data);
and then your js would be somthing like:
success: function (result) {
if (result.results == 'success') {
alert(result.message);
} else if (result.results == 'errors' {
alert(result.message);
}
},
related : http://www.dyn-web.com/tutorials/php-js/json/array.php#assoc