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Valentina
Asked: 2020-10-02 00:16:46 +0800 CST 2020-10-02 00:16:46 +0800 CST

Error in detecting URL from a loop/while

  • 772

In my database it is allowed to enter images locally -> imagen.pngor from one URL-> https://dominio/ruta/imagen.png, the main idea is to be able to detect if said data starts with: http, https, ftp.

Using the following code I get that response without any problem:

$image = "http://www.example.com";

$UrlImage = $image;
if(preg_match('/^(http|ftp|https)\:\/\/+[a-z0-9\.\_-]+$/i',$UrlImage)) {
    //echo '<img src="'.$image.'">';
    echo 'URL';
} else {
    //echo '<img src="assets/img/website/catalog/'.$image.'">';
    echo 'No URL';
}

It should be noted that the variable $imagecan store two values ​​local image 1.pngor image urlhttp://dominio/ruta/1.png

The error

When executing said example inside a loop, whileit shows me as a result that everything is No URLeven the one that if they are , URLit shows me that it is No URL, this is my code:

$stmt->bind_result(
                    $id_product,
                    $image,
                    $product
);

while ($stmt->fetch()) {

    $UrlImage = $image;
    
    if(preg_match('/^(http|ftp|https)\:\/\/+[a-z0-9\.\_-]+$/i',$UrlImage)) {
        //echo '<img src="'.$image.'">';
        echo 'URL';
    } else {
        //echo '<img src="assets/img/website/catalog/'.$image.'">';
        echo 'No URL';
    }
}

Can you tell me how to solve the problem, what am I doing wrong?

php

2 Answers

  1. Best Answer

    The error is in the regular expression you used

    /^(http|ftp|https)\:\/\/+[a-z0-9\.\_-]+$/i

    which will clearly match a domain-only URL, as in "http://www.example.com", but will not match a longer path as in "http://dominio/ruta/1.png"

    Why? Because a-z0-9._-they are the allowed characters, and it does not contain the /within them.

    Instead, if we add it to that character class, the following expression will match:

    /^(https?|ftp):[-a-z0-9._\/]+$/i

    Another way to validate URLs, without worrying about regex syntax, is to use filter_var() :

    if (filter_var($UrlImage, FILTER_VALIDATE_URL) !== false) {
    echo 'URL válida';
}

    and in case it helps you can also pass options as 3rd parameter to filter_var():

    FILTER_FLAG_SCHEME_REQUIRED   Sólo si respeta el RFC
FILTER_FLAG_HOST_REQUIRED     Debe contener el dominio (www.ejemplo.com)
FILTER_FLAG_PATH_REQUIRED     Debe contener una ruta (/ruta/archivo.html)
FILTER_FLAG_QUERY_REQUIRED    Debe contener parámetros de consulta (?a=busqueda)
    • 4

  2. Sorry to differ from the second part of @Pollo's answer regarding the use of filter_var(), as this function would consider a URL like this to be valid: ttp://www.example.com. Also, the intention is not to actually validate a URL, but to check if it starts with http, httpsor ftp.

    If you want to avoid using regular expressions, this could easily be done using parse_url(). By passing the flag PHP_URL_SCHEMEyou would get only the first part of the URL and you could check the data against an array containing the values ​​of your whitelist using in_array().

    The code would look like this:

    $UrlImage = 'https://www.example.com';
$whiteList=array('https','http','ftp'); 
if (in_array(parse_url($UrlImage, PHP_URL_SCHEME), $whiteList)) {
    echo "Ok"; #Actuar en consecuencia
}

    To simplify and/or create portable code , you can create a function that returns a boolean and call it from within the loop, something like this:

    function isSchemaValid($url) {
    $whiteList=array('https','http','ftp'); 
    return (in_array(parse_url($url, PHP_URL_SCHEME), $whiteList)); 
}

    If whitelists vary by context you can take it out $whiteListof the function and put it as a parameter, then you would declare $whiteListin the context.

    To use the function in the loop:

    while ($stmt->fetch()) {    
    if(isSchemaValid($image)) {
        //echo '<img src="'.$image.'">';
        echo 'URL';
    } else {
        //echo '<img src="assets/img/website/catalog/'.$image.'">';
        echo 'No URL';
    }
}

    OBSERVE that in whileI am passing $imageto the function, since it is redundant to do this: $UrlImage = $image; , because you already have the data in $image.

    • 1