curl_getinfo

Here are the response codes ready for pasting in an ini-style file. Can be used to provide more descriptive message, corresponding to 'http_code' index of the arrray returned by curl_getinfo(). 
These are taken from the W3 consortium HTTP/1.1: Status Code Definitions, found at
http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

[Informational 1xx]
100="Continue"
101="Switching Protocols"

[Successful 2xx]
200="OK"
201="Created"
202="Accepted"
203="Non-Authoritative Information"
204="No Content"
205="Reset Content"
206="Partial Content"

[Redirection 3xx]
300="Multiple Choices"
301="Moved Permanently"
302="Found"
303="See Other"
304="Not Modified"
305="Use Proxy"
306="(Unused)"
307="Temporary Redirect"

[Client Error 4xx]
400="Bad Request"
401="Unauthorized"
402="Payment Required"
403="Forbidden"
404="Not Found"
405="Method Not Allowed"
406="Not Acceptable"
407="Proxy Authentication Required"
408="Request Timeout"
409="Conflict"
410="Gone"
411="Length Required"
412="Precondition Failed"
413="Request Entity Too Large"
414="Request-URI Too Long"
415="Unsupported Media Type"
416="Requested Range Not Satisfiable"
417="Expectation Failed"

[Server Error 5xx]
500="Internal Server Error"
501="Not Implemented"
502="Bad Gateway"
503="Service Unavailable"
504="Gateway Timeout"
505="HTTP Version Not Supported"

And an example usage:
<?php
$ch = curl_init(); // create cURL handle (ch)
if (!$ch) {
    die("Couldn't initialize a cURL handle");
}
// set some cURL options
$ret = curl_setopt($ch, CURLOPT_URL,            "http://mail.yahoo.com");
$ret = curl_setopt($ch, CURLOPT_HEADER,         1);
$ret = curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
$ret = curl_setopt($ch, CURLOPT_RETURNTRANSFER, 0);
$ret = curl_setopt($ch, CURLOPT_TIMEOUT,        30);

// execute
$ret = curl_exec($ch);

if (empty($ret)) {
    // some kind of an error happened
    die(curl_error($ch));
    curl_close($ch); // close cURL handler
} else {
    $info = curl_getinfo($ch);
    curl_close($ch); // close cURL handler

    if (empty($info['http_code'])) {
            die("No HTTP code was returned"); 
    } else {
        // load the HTTP codes
        $http_codes = parse_ini_file("path/to/the/ini/file/I/pasted/above");
        
        // echo results
        echo "The server responded: <br />";
        echo $info['http_code'] . " " . $http_codes[$info['http_code']];
    }

}
?>

CURLINFO_HTTP_CODE does not return a string, as the docs say, but rather an integer.

<?php
    $c = curl_init('http://www.example.com/');
    if(curl_getinfo($c, CURLINFO_HTTP_CODE) === '200') echo "CURLINFO_HTTP_CODE returns a string.";
    if(curl_getinfo($c, CURLINFO_HTTP_CODE) === 200) echo "CURLINFO_HTTP_CODE returns an integer.";
    curl_close($c);
?>

returns

"CURLINFO_HTTP_CODE returns an integer."

CURLINFO_SSL_VERIFYRESULT error codes:
0: ok the operation was successful. 
2 : unable to get issuer certificate
3: unable to get certificate CRL
4: unable to decrypt certificate's signature
5: unable to decrypt CRL's signature
6: unable to decode issuer public key
7: certificate signature failure
8: CRL signature failure
9: certificate is not yet valid
10: certificate has expired
11: CRL is not yet valid
12:CRL has expired
13: format error in certificate's notBefore field
14: format error in certificate's notAfter field
15: format error in CRL's lastUpdate field
16: format error in CRL's nextUpdate field
17: out of memory
18: self signed certificate
19: self signed certificate in certificate chain
20: unable to get local issuer certificate
21:unable to verify the first certificate
22: certificate chain too long
23: certificate revoked
24: invalid CA certificate
25: path length constraint exceeded
26: unsupported certificate purpose
27: certificate not trusted
28: certificate rejected
29: subject issuer mismatch
30: authority and subject key identifier mismatch
31: authority and issuer serial number mismatch
32: key usage does not include certificate signing
50: application verification failure
details at http://www.openssl.org/docs/apps/verify.html#VERIFY_OPERATION

Here you have a function that I use to get the content of a URL using cURL. This uses curl_getinfo to know if it is a regular URL or maybe a redirection.

I hope it would be useful for you:

function getUrlContent($url){
 $ch = curl_init();
 curl_setopt($ch, CURLOPT_URL, $url);
 curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322)');
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);
 curl_setopt($ch, CURLOPT_TIMEOUT, 5);
 $data = curl_exec($ch);
 $httpcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
 curl_close($ch);
 return ($httpcode>=200 && $httpcode<300) ? $data : false;
}

The source comes from this website:

http://softontherocks.blogspot.com/2014/11/descargar-el-contenido-de-una-url.html

Note, header_size include "\r\n\r\n". So if you use CURLOPT_FOLLOWLOCATION>0, CURLOPT_HEADER=true, CURLOPT_RETURNTRANSFER=true right way splite header/body:

$response = curl_exec($ch);
$curl_info = curl_getinfo($ch);
curl_close($ch);
$header_size = $curl_info['header_size'];
$header = substr($response, 0, $header_size);
$body = substr($response, $header_size);

Just a quick note: if you want to use curl_getinfo() with option CURLINFO_HEADER_OUT in order to debug your cURL request, you must add curl_setopt($handle, CURLINFO_HEADER_OUT, true); first while specifying the options.

curl_getinfo($ch) will also return 'redirect_url' if there is one (even if CURLOPT_FOLLOWLOCATION set to false).
I don't know why it's not in the doc..

There is a constant missing from that list.  CURLINFO_REDIRECT_COUNT will give you the number of redirects it went through if CURLOPT_FOLLOWLOCATION was set.

Люди подскажите Близкий человек уже несколько дней в запое Родственники не знают что делать В больницу тащить страшно Короче, врачи приехали и поставили систему — нарколог запой щелково с опытом Приехали через 40 минут В общем, жмите чтобы сохранить — вывод из запоя щёлково <a href=https://anonimnyj.vyvod-iz-zapoya-na-domu-moskva-snp.ru>вывод из запоя щёлково</a> Не ждите пока станет хуже Перешлите тем кто в такой же ситуации

Здорова, народ Близкий человек уже несколько дней в запое Родственники не знают что делать Таблетки не помогают Короче, единственное что вытащило из запоя — вывод из запоя люберцы с выездом Сняли ломку и стабилизировали состояние В общем, телефон и цены тут — вывод из запоя <a href=https://stoimost.vyvod-iz-zapoya-na-domu-moskva-jst.ru>https://stoimost.vyvod-iz-zapoya-na-domu-moskva-jst.ru</a> Вывод из запоя на дому — это реальный выход Перешлите тем кто в такой же ситуации

More https://vc.ru/id3219783/2886181-kak-ya-obnovil-svoy-lichnyy-sayt-vizitku

You can still get the SSL verification result using CURLINFO_SSL_VERIFYRESULT when setting CURLOPT_SSL_VERIFYPEER to FALSE.

Full list of result codes:

0: ok
1: unspecified certificate verification error
2: unable to get issuer certificate
3: unable to get certificate CRL
4: unable to decrypt certificate's signature
5: unable to decrypt CRL's signature
6: unable to decode issuer public key
7: certificate signature failure
8: CRL signature failure
9: certificate is not yet valid
10: certificate has expired
11: CRL is not yet valid
12: CRL has expired
13: format error in certificate's notBefore field
14: format error in certificate's notAfter field
15: format error in CRL's lastUpdate field
16: format error in CRL's nextUpdate field
17: out of memory
18: self-signed certificate
19: self-signed certificate in certificate chain
20: unable to get local issuer certificate
21: unable to verify the first certificate
22: certificate chain too long
23: certificate revoked
24: issuer certificate doesn't have a public key
25: path length constraint exceeded
26: unsuitable certificate purpose
27: certificate not trusted
28: certificate rejected
29: subject issuer mismatch
30: authority and subject key identifier mismatch
31: authority and issuer serial number mismatch
32: key usage does not include certificate signing
33: unable to get CRL issuer certificate
34: unhandled critical extension
35: key usage does not include CRL signing
36: unhandled critical CRL extension
37: invalid non-CA certificate (has CA markings)
38: proxy path length constraint exceeded
39: key usage does not include digital signature
40: proxy certificates not allowed, please set the appropriate flag
41: invalid or inconsistent certificate extension
42: invalid or inconsistent certificate policy extension
43: no explicit policy
44: different CRL scope
45: unsupported extension feature
46: RFC 3779 resource not subset of parent's resources
47: permitted subtree violation
48: excluded subtree violation
49: name constraints minimum and maximum not supported
50: application verification failure
51: unsupported name constraint type
52: unsupported or invalid name constraint syntax
53: unsupported or invalid name syntax
54: CRL path validation error
55: path loop
56: Suite B: certificate version invalid
57: Suite B: invalid public key algorithm
58: Suite B: invalid ECC curve
59: Suite B: invalid signature algorithm
60: Suite B: curve not allowed for this LOS
61: Suite B: cannot sign P-384 with P-256
62: hostname mismatch
63: email address mismatch
64: IP address mismatch
65: no matching DANE TLSA records
66: EE certificate key too weak
67: CA certificate key too weak
68: CA signature digest algorithm too weak
69: invalid certificate verification context
70: issuer certificate lookup error
71: Certificate Transparency required, but no valid SCTs found
72: proxy subject name violation
73: OCSP verification needed
74: OCSP verification failed
75: OCSP unknown cert
76: Cannot find certificate signature algorithm
77: subject signature algorithm and issuer public key algorithm mismatch
78: cert info signature and signature algorithm mismatch
79: invalid CA certificate
80: Path length invalid for non-CA cert
81: Path length given without key usage keyCertSign
82: Key usage keyCertSign invalid for non-CA cert
83: Issuer name empty
84: Subject name empty
85: Missing Authority Key Identifier
86: Missing Subject Key Identifier
87: Empty Subject Alternative Name extension
89: Basic Constraints of CA cert not marked critical
88: Subject empty and Subject Alt Name extension not critical
90: Authority Key Identifier marked critical
91: Subject Key Identifier marked critical
92: CA cert does not include key usage extension
93: Using cert extension requires at least X509v3
94: Certificate public key has explicit ECC parameters
95: Raw public key untrusted, no trusted keys configured

source: https://github.com/openssl/openssl/blob/master/include/openssl/x509_vfy.h.in
https://github.com/openssl/openssl/blob/master/crypto/x509/x509_txt.c

A note about $curl_info['header_size'] (in response to the example above). 

Note that the total includes the size of any received headers suppressed by CURLOPT_SUPPRESS_CONNECT_HEADERS (see: https://curl.se/libcurl/c/CURLINFO_HEADER_SIZE.html) so if you are using a proxy which adds additional headers along with this option, $curl_info['header_size'] will give you the wrong string index based on the headers available in PHP. i.e., it will eat in to the start of the response instead of being the index of the beginning of the response.

If you use curl option CURLOPT_NOBODY = true to test if distant url is available, any sites can send you an http code 400 like Cdiscount Wsdl : 

$ch = @curl_init($wsdl);

if($ch === false)
    return false;
        
@curl_setopt($ch, CURLOPT_HEADER         ,true);    // we want headers
@curl_setopt($ch, CURLOPT_NOBODY         ,true);    // dont need body
@curl_setopt($ch, CURLOPT_RETURNTRANSFER ,true);    // catch output (do NOT print!)

@curl_exec($ch);

if(@curl_errno($ch)){   // should be 0
    @curl_close($ch);
    return false;
}

$code = @curl_getinfo($ch, CURLINFO_HTTP_CODE); 

Modifying CURLOPT_NOBODY to false, http code sent is 200 otherwise http code is 400 !!!

The main doc neglects to mention that when the CURLINFO_HEADER_OUT option is set the array returned by this function will included a new property, request_header, that is a string of the headers sent in the request.

If you call curl_reset() on a handle that has already been passed to curl_exec(), and then perform a curl_getinfo() on the same handle, you may expect that you get the same result as if you called curl_getinfo() immediately after curl_init(). This is not the case, however. cURL will return the data from the previous execution. If you want to completely reset you actually need to unset the cURL handle and recreate a new one.